I-  /  \  >  '    '  >f  1    t.t    t  r^r~ 

AND 

PHOTOMECIL^IICL'oj 
PROCESSES 


:'7:r'.\ 

Digitized  by  the  Internet  Archive 
in  2014 


https://archive.org/details/horganshalftonepOOhorg 


PHOTOGRAVURE. 
Portrait  of  the  Author. 


H0RGAN5  HALF-TONE 

AND 

PHOTOMECHANICAL 

3y  STEPHEN  H.HORGANT 


PUBLISHED  BY 
THE  INLAND  PRINTER  COMPANY 
CHICAGO 


Copyright,  1913. 
The  Inland  Printer  Company. 


PREFACE. 


It  was  the  writer's  fortune  to  witness  the  culmination  of 
what  may  be  termed  the  Golden  Age  of  Wood  Engraving  in 
the  United  States;  to  be  present  at  the  birth  of  photo- 
engraving; to  have  taken  an  active  part  in  the  struggle  for 
supremacy  between  wood  engraving  and  photoengraving; 
to  regretfully  witness  the  decline  of  wood  engraving,  and  to 
contribute  somewhat  to  the  success  and  popularizing  of 
what  is  now  included  in  the  generic  term,  "  Processwork." 
Now  that  manual  engraving  has  surrendered  and  photo- 
mechanical engraving  occupies  the  field,  it  has  been  sug- 
gested that  the  writer  put  on  record  some  of  the  knowledge 
gained  through  his  unique  experience. 

The  contest  began  with  the  appearance  of  the  first  illus- 
trated daily  newspaper  in  the  world.  This  was  on  March  4, 
1873,  when  the  New  York  Daily  Graphic  issued  its  first 
copy.  Artists,  engravers,  publishers,  printers  everywhere 
were  startled  by  the  boldness  of  what  they  thought  was  but 
an  experiment.  Still  the  Graphic  lived  for  eighteen  years. 
It  raised  up  a  school  of  illustrators  that  became  pioneers  in 
the  newer  methods,  and  taught  that  the  camera  was  the 
future  medium  for  introducing  illustrations  to  the  printing- 
press. 

In  1874  the  writer  was  initiated  into  the  mysterious 
chambers  where  the  Graphic  processes  were  worked  behind 
locked  and  barred  doors.  From  that  day  his  life  has  been 
given  to  the  study  of  all  the  methods  by  which  photography 
could  be  applied  to  producing  pictures  in  printing-ink.  Many 
of  these  methods  he  has  put  into  practice. 

During  the  past  eighteen  years  it  has  been  the  writer's 
pleasure  to  contribute  from  his  storehouse  of  experience  to 
those  who  ask  for  information  regarding  the  photomechan- 
ical printing  processes,  through  the  columns  of  The  Inland 
Printer.  Reciprocity  has  resulted.  There  has  been  an 
interchange  of  knowledge,  and  he  has  learned,  among  other 


ii 


iiorgan's  half-tone 


things,  what  are  the  subjects,  relating  to  processwork,  on 
which  there  is  most  frequently  a  demand  for  light. 

These  queries  came  from  the  journeyman  engraver  as 
well  as  the  apprentice;  from  artists,  employing  engravers, 
publishers,  printers,  advertisers,  investors  of  capital  and  the 
varied  classes  who  read  The  Inland  Printer.  So  one 
object  of  this  book  has  been  to  combine  in  one  volume,  in  a 
brief  way,  the  information  most  desired. 

Nothing  theoretical  is  recorded.  All  the  processes  and 
formulas  as  given  have  been  evolved  by  practical  use.  Many 
of  them  have  cost  a  fortune,  together  with  years  of  experi- 
ment, to  develop.  They  follow  in  the  book  in  something  like 
the  order  in  which  they  came  into  use.  Preference  has  been 
given  to  the  methods  that  have  survived,  those  that  have 
proved  entirely  practical  and  are  either  in  use  to-day  or  are 
merely  awaiting  application.  An  account  of  the  photo- 
mechanical printing  processes  that  have  been  tried  and  found 
wanting  would  fill  many  volumes,  yet  some  space  has  been 
given  to  them  here  for  the  reason  that  many  of  them  are 
being  rediscovered  by  beginners  at  processwork.  These 
tyros,  thinking  they  have  an  important  discovery,  interest 
capital  only  to  find  later,  after  much  waste  of  energy  and 
money,  that  they  are  trying  to  resurrect  a  corpse. 

If  the  student  of  processwork  will  begin  with  photo- 
lithography and  master  that  process  he  will  possess  a  knowl- 
edge of  the  underlying  principles  in  all  of  the  photomechan- 
ical printing  methods  and  particularly  as  regards  negative- 
making,  which,  after  all,  is  the  basis  for  good  processwork 
of  any  description.  The  index  will  guide  the  reader  to  the 
information  he  is  seeking,  and  the  perplexed  process  worker 
to  a  way  out  of  his  troubles ;  while  a  study  of  the  illustra- 
tions, with  a  magnifying  glass,  will  enable  any  one  to  learn 
to  distinguish  the  varied  processes  that  contribute  the  pic- 
tures which  illuminate  printed  matter  to-day. 

Gratitude  is  herewith  expressed  to  those  who  so  willingly 
contributed  the  splendid  educational  exhibits  of  their  work. 
These  illustrations  were  not  selected  for  their  attractiveness 
(the  pictures  of  the  gentle  sex,  of  course,  excepted),  but  for 


PREFACE 


111 


their  technical  value,  which  will  be  appreciated  by  the  stu- 
dent. Wood,  steel  and  wax  engraving ;  needle-point  etching, 
mezzotint,  aquatint  and  the  manual  methods  of  engraving 
are  of  course  omitted  because  photography  does  not  neces- 
sarily enter  into  their  production. 

As  to  the  future  of  processwork  —  there  is  no  one  suffi- 
ciently prophetic  to  predict  it.  It  is  conceded  that  it  has 
been  one  of  the  principal  factors  in  popularizing  the  product 
of  the  printing-press,  thus  spreading  knowledge  and  hasten- 
ing progress.  It  has  also  created  enormous  lines  of  new 
business,  introduced  special  kinds  of  paper,  ink,  and  much 
improved  presses.  The  exhibits  of  the  offset  press  and 
rotary  photogravure  in  this  volume  point  in  the  direction  of 
future  conquests.  That  it  is  destined  to  wider,  better,  higher 
achievement  is  inevitable,  as  Tennyson's  lines  come  to  mind : 


Not  in  vain  the  distance  beacons.  Forward, 

Forward  let  us  range ; 
Let  the  great  world  spin  forever  down  the 

Ringing  grooves  of  change. 

Yet  I  doubt  not  through  the  ages  one 

Increasing  purpose  runs, 
And  the  thoughts  of  men  are  broadened  by 

THE  PROCESS  OF  THE  SUNS. 


CONTENTS. 

PAGES 

Engravers'  and  Printers'  Exhibits  5-10 

Photolithography  Applied  to  Stone  or  Metal  11-40 

Collotype   41-45 

Colloids  Used  —  Gelatin,  Isinglass  46 

Photogravure  47-60 

Moss  Process  of  Swelled-gelatin  Relief  61-62 

Photoelectrotype  63-68 

Relief-line  Engraving  69-84 

Half-tone  Process   85-109 

Half-tone  Engravers  Should  Know  109-110 

Three-color  and  Four-color  Blockmaking  111-132 

Photoplanography  for  the  Offset  Press  133-144 

Rotary  Photogravure   145-153 

Transferring  Enamel  to  a  Roll  153-154 

Facts  for  Every  Process  Photographer  155-164 

Zinc  and  Copper  Etchers'  Formulas,  Methods  165-170 

For  Foremen,  Finishers,  Journeymen  171-176 

Pointers  for  the  Photographer  177-179 

Bichromate  Poisoning  Remedies  180 

Proper  Care  of  a  Lithographic  Roller  181-182 

Negatives  Etched  by  Hand  183-185 

Screens  and  Their  Care  185-186 

Processworkers  May  Be  Jailed  187-188 

"  Direct  Process  "  with  Norwich  Film  189 

Key-plates,  to  Photograph  on  Zinc  190 

Weights  and  Measures  191 

Metric  Measures  Converted  Into  English  192 

Thermometer  Comparisons   193 

Poisons,  Symptoms  and  Antidotes  194-195 

Chemicals  in  English,  Latin,  German  and  French  196-197 

Chemical  Symbols  and  Solubilities  198-199 

Exposures  Affected  by  Focus  and  Stop  200 

Glossary  of  Process  Terms  201-222 

iv 


THE  ILLUSTRATIONS  IN  THIS  VOLUME 


AND 

THE  ENGRAVERS  AND  PRINTERS  TO  WHOM  CREDIT  IS 
DUE  FOR  THE  EXHIBITS  OF  PHOTOMECHANICAL 
PRINTING  PROCESSES. 


AUTOCHROME  REPRODUCTION  IN  THREE  PRINTINGS. 

This  is  "the  last  word"  in  reproducing  in  printing-ink  the 
colors  of  nature.  And  it  is  most  appropriate  that  the  subject  of 
the  picture  should  be  M.  Louis  Lumiere,  one  of  the  famous  brothers 
of  Lyons,  France,  to  whom  the  invention  of  the  Autochrome  system 
of  photography  in  colors  is  due.  The  reproduction  of  the  auto- 
chrome into  three  printing-plates,  as  well  as  the  printing,  is  by 
J.  Horace  McFarland,  of  Harrisburg,  Pennsylvania. 

BOOK  STAMPS  FOR  THE  COVER. 
Here  is  a  little-known  application  of  photoengraving.  The  half- 
tone screen  enlargement,  used  as  a  band  around  the  cover,  and  the 
lettering  in  gold,  were  stamped  from  brass  plates  one-quarter  inch 
in  thickness.  The  designs  were  photographed  upon  the  brass  plates 
when  sensitized  with  an  enamel.  They  were  etched  in  an  etching 
machine.  These  plates  are  known  as  book  stamps  for  hot-press  work, 
and  are  a  specialty  with  The  Photo-Chromotype  Company,  of  Phila- 
delphia, who  supplied  them. 

COLLOTYPE. 

"  Bed  Time  Stories  "  was  printed  direct  from  gelatin  on  a  steam 
press  by  the  Autogravure  Company,  of  New  York.  This  process, 
while  equaling  a  photograph  in  quality,  has  the  advantage  that  it  is 
printed  in  a  permanent  printing-ink.  It  is  one  of  the  photomechan- 
ical printing  processes  much  neglected  by  publishers  through  want 
of  knowledge  of  its  possibilities.  A  chapter  on  Collotype  will  be 
found  on  page  41. 

COMBINATION  PLATE. 

Scenes  recalling  Paul  Revere's  famous  ride  are  contributed  by 
the  Folsom  &  Sunergren  Company,  of  Boston.  The  border  and 
the  several  scenes  inserted  in  it  were  photographed  from  different 
copies  and  the  negatives  combined  in  one  plate,  hence  the  name 
"  Combination  Plate."  Paul  Revere  was  the  earliest  American  engra- 
ver and  the  first  one  to  roll  copper  into  sheets,  so  that  he  is  a  sort 
of  patron  saint  of  American  engravers. 


v 


vi 


horgan's  half-tone 


"  DIRECT  PROCESS  "  WITH  NORWICH  FILM. 

This  is  an  extremely  simple  engraving  method  by  which  the 
drawing  of  the  artist  can  be  used  as  a  positive  for  intaglio  engra- 
ving or  turned  into  a  negative  for  relief  engraving  or  planographic 
printing.  This  engraving  was  made  by  the  inventor,  Ozias  Dodge, 
of  Norwich,  Connecticut.   The  process  is  described  on  page  189. 

DUOGRAPH,  WITH  MEZZOGRAPH  SCREEN. 

The  portrait  of  "A  Sweet  Girl  Graduate"  is  printed  from  a 
half-tone  with  a  mezzograph  tint-plate.  The  grain  of  the  mezzo- 
graph  screen  underneath  breaks  up  the  mechanical  character  of  the 
screen  half-tone  with  a  most  pleasing  result.  This  style  of  engra- 
ving is  not  in  use  to  the  extent  it  should  be.  These  plates  are 
from  Gatchell  &  Manning,  Philadelphia,  Pennsylvania. 

DUOGRAPH. 

The  portrait  of  Louis  J.  M.  Daguerre,  who  gave  to  the  world 
the  Daguerreotype  process,  January  9,  1839,  is  from  a  daguerreotype 
made  in  1846.  Here  are  shown  two  half-tone  plates  made  at  dif- 
ferent angles  to  each  other  and  the  two  printings  superimposed. 
The  plates  are  from  one  of  the  oldest  photoengraving  firms  in  Amer- 
ica, the  Electro-Light  Engraving  Company,  of  New  York. 

FIRST  PHOTOENGRAVING. 

This  portrait  of  Cardinal  d'Amboise  is  famous  through  being 
the  earliest  photoengraving  known.  The  plate  was  engraved, 
through  the  aid  of  bitumen  or  asphalt,  by  Joseph  Nicephore  Niepce, 
in  1824.  The  original  plate  is  still  in  the  museum  at  Chalons, 
France.  An  impression  from  the  original  plate  is  in  the  Smith- 
sonian Institution,  Washington.  It  was  reproduced  by  Mr.  Albert 
H.  Walker,  of  New  York,  and  from  the  latter  The  Barnes-Crosby 
Company,  of  Chicago,  produced  the  marvelous  reproduction  shown 
here.  This  company  specializes  in  every  branch  of  processwork,  so 
that  this  plate  may  be  said  to  be  the  acme  of  relief-plate  line  engra- 
ving. Every  detail  and  defect  in  the  reproduction  of  Niepce's 
engraving  is  faithfully  preserved. 

FOUR-COLOR  PROCESS  BLOCKS. 

"  An  Engraver,"  from  the  picture  by  Paul  Mathey  in  the  Musee 
du  Luxembourg,  Paris.  This  most  beautiful  reproduction  in  colors 
is  worthy  of  careful  study  with  a  microscope.  It  will  be  noticed 
that  the  screens  used  are  160  lines  to  the  inch.    The  blue  plate  is 


ILLUSTRATIONS. 


vii 


from  a  single  line  screen  with  the  lines  running  vertically ;  the  red 
is  also  made  through  a  single  line  screen  with  the  lines  horizontal. 
The  yellow  plate  is  from  a  cross-line  screen  with  one  of  the  lines 
printing  at  an  angle  of  22^  degrees,  while  the  gray,  or  black  plate, 
is  also  from  a  cross-line  screen  printed  at  an  angle  of  45  degrees. 
These  color  blocks  were  engraved  expressly  for  this  volume  by 
John  Swain  &  Son,  Ltd.,  London.  See  "  Three-color  Process- 
work,"  page  in. 

HALF-TONE  OF  1868. 

The  original  steel-plate  engraving,  from  which  this  is  enlarged 
almost  twice,  was  made  by  Gen.  Frederick  W.  Von  Egloff stein  at 
125  West  Twenty-fifth  street,  New  York,  in  1868.  It  will  be  noticed 
that  a  wavy-line  screen  was  used.  The  excellent  reproduction  is  by 
F.  A.  Ringler  Company,  New  York. 

HALF-TONE  WITH  TWO-HUNDRED-LINE  SCREEN. 

The  latest  portrait  of  Mr.  Frederic  E.  Ives,  by  the  Suffolk 
Engraving  Company,  of  New  York  and  Boston,  is  appropriately 
enough  made  with  the  finest  screen  that  can  be  successfully  used  in 
printing.  Mr.  Ives  has  contributed  more  than  any  other  individual 
to  make  practical  the  half-tone  screen  and  its  method  of  use 
employed  to-day.   The  "Half-tone  Process"  is  described  on  page  85. 

HIGH-LIGHT  HALF-TONE. 

The  Walker  Engraving  Company,  of  New  York,  exhibit  here 
the  highest  point  that  photoengraving  has  reached  at  this  time. 
This  high-light  half-tone  was  made  from  a  drawing  by  Vernon 
Howe  Bailey,  copyrighted  by  Harper  &  Bros.  Every  processworker 
will  appreciate  the  delicacy  of  the  engraving  and  the  vignetting. 
High-light  half-tone  negative  making  is  described  on  page  144. 

HIGH-LIGHT  HALF-TONE  OF  1880. 

The  writer  began  experimenting  with  half-tone  in  1876.  Though 
with  little  time  at  his  disposal,  he  devised  a  practical  half-tone 
process  which  was  first  shown  in  the  New  York  Daily  Graphic,  of 
March  4,  1880,  with  a  picture  titled  "  Shanty  Town."  The  endeavor 
in  those  days  was  to  get  a  "  full-tone,"  that  is,  a  picture  graded 
from  solid  blacks  in  the  deepest  shadows  to  pure  whites  in  the 
extreme  high  lights,  for  the  reason  that  there  was  no  coated  paper 
in  those  days  and  the  presses  and  printers  had  not  arrived  to  print 
half-tones  as  experience  has  taught  to-day.  The  half-tone  here 
shown  was  made  in  February,  1880,  and  the  excellent  reproduction 
of  it  was  made  by  the  General  Engraving  Company,  of  New  York. 


viii 


horgan's  half-tone 


LINE  PHOTOENGRAVING. 

This  most  important  branch  of  photoengraving  has  been  neg- 
lected since  half-tone  engraving  has  become  so  popular.  The  illustra- 
tion is  a  suggestion  for  a  statue  to  Gen.  William  T.  Sherman,  by 
James  E.  Kelly,  the  sculptor.  Mr.  Kelly  it  was  who  first  introduced 
outline  drawing  to  the  magazines  of  this  country.  The  reproduction 
of  his  most  delicate  sketch  is  by  the  Globe  Engraving  &  Electrotyp- 
ing  Company,  of  Chicago.  A  chapter  is  given  to  "  Relief-line  Engra- 
ving," beginning  page  69. 

MEZZOGRAPH. 

A  portrait  bust  of  Joseph  Nicephore  Niepce,  the  first  photo- 
engraver.  Niepce  was  born  at  Chalon-sur-Saone,  March  7,  1765, 
and  died  July  5,  1833.  Discovering  that  asphalt  was  sensitive  to  light, 
he  made,  in  1822,  photographic  prints  upon  tin  with  it.  In  1824  he 
made  the  first  camera  picture.  His  first  photoengraving  was  also 
made  this  year,  a  reproduction  of  which  is  given  in  this  volume.  This 
mezzograph  engraving  was  made  by  the  Cincinnati  Process  Engra- 
ving Company,  of  Cincinnati.  Paragraphs  treating  on  the  mezzo- 
graph  screen  will  be  found  on  page  186. 

NEGATIVE  ETCHED  ON  GLASS. 

On  page  183  is  described  the  method  of  etching  negatives  with 
needle  points.  The  portrait,  made  from  an  etched  negative,  is  that 
of  the  Hon.  Charles  O'Conor,  from  the  New  York  Daily  Graphic, 
of  June  26,  1873.  Charles  O'Conor  was  New  York's  leading  lawyer 
and  is  said  to  "  have  never  lost  a  case."  The  reproduction  testifies 
to  the  skill  of  the  Farmer-Zehr  Engraving  Company,  of  New  York. 

NEWSPAPER  HALF-TONE. 

The  American  Press  Association  contributed  the  exhibit  of 
the  best  there  is  in  newspaper  illustration  to-day.  The  writer 
founded,  in  1884,  the  art  and  engraving  departments  of  this  asso- 
ciation, and  when  the  history  of  illustrated  journalism  comes  to  be 
written  it  will  be  found  that  this  department  pioneered  and  set  the 
style  for  modern  newspaper  illustrations  in  America,  and  conse- 
quently for  the  whole  world. 

OFFSET  PRINTING  IN  COLOR. 

The  beautiful  insert  showing  a  girl  of  the  period  proves  the 
infinite  possibilities  of  the  offset  press  in  rendering  color  effects. 
This  has  the  quality  of  the  pastel.  It  is  accomplished  in  nine  print- 
ings and  is  called  an  "aquatint"  by  The  Knapp  Company,  New 
York,  who  supplied  the  inserts.  The  chapter  on  "  Photoplanography," 


ILLUSTRATIONS. 


ix 


on  page  133,  describes  the  application  of  photography  to  the  offset 
press. 

OFFSET-PRESS  WORK  IN  ONE  PRINTING. 

Gies  &  Co.,  of  Buffalo,  have  given  one  of  the  best  answers  to 
the  critics  of  the  offset  press  in  this  beautiful  insert  which  they  have 
supplied,  showing  impressions  on  both  sides  of  rough-surfaced  paper. 
It  proves  that  the  success  of  the  offset  press  depends  upon  the 
"man  behind  the  gun,"  and  the  Gies  Company  have  picked  gun 
crews.  The  softness  and  delicacy  of  gradation  of  tones  shown  here 
will  be  a  revelation  to  many.    See  "  Photoplanography,"  page  133. 

PHOTOELECTROTYPE. 

With  our  increased  knowledge,  improved  lenses  and  processes, 
it  is  doubtful  whether  we  could  improve  on  this  photoelectrotype 
portrait  of  Mr.  F.  A.  Ringler.  This  portrait  is  printed  from  an 
electrotype  made  about  1890.  The  process  is  well  described  on 
page  63. 

PHOTOGRAVURE. 

The  frontispiece  was  made  by  Mr.  W.  H.  Gilbo,  of  Brooklyn, 
New  York,  a  pioneer  in  engraving  photogravure  plates  in  the 
United-  States.  When  the  illustrations  printed  on  coated  paper  have 
all  crumbled  to  dust  in  this  volume,  the  photogravure  will  be  still  in 
good  condition.  It  is  a  reflection  on  the  taste  of  the  American  public 
that  photogravure  is  not  more  popular.  On  page  47  will  be  found  a 
chapter  devoted  to  "  Photogravure." 

PHOTOLITHOGRAPHY. 

The  map  photolithographed  by  Leggo  Bros.  &  Co.,  of  New  York, 
and  printed  by  Charles  Hart,  lithographer,  also  of  New  York, 
will  be  a  surprise  to  those  who  are  unacquainted  with  the  beauties 
of  this  oldest  of  the  practical  photomechanical  processes.  There 
is  no  engraving,  routing,  underlaying  or  overlaying  on  this  work. 
It  is  an  exact  reproduction  of  the  artist's  drawing.  The  map  is  from 
"  A  Text  Book  on  Plain  Lettering,"  by  courtesy  of  the  author, 
Prof.  Henry  S.  Jacoby,  of  Ithaca,  New  York.  The  opening  chapter 
in  our  volume,  page  II,  goes  into  the  details  of  photolithography  for 
the  first  time. 

FIRST  PHOTO-RELIEF  ENGRAVING. 

Paul  Pretsch  patented  in  England,  on  November  9,  1854,  his 
process  for  making  printing-plates  from  gelatin  swelled  into  relief. 
He  sensitized  the  gelatin  with  nitrate  of  silver,  iodid  of  potassium 
and  bichromate  of  potash,  and  reticulated  the  gelatin  afterward  with 
a  solution  of  tannin  in  alcohol.    He  then  either  cast  in  plaster  and 


X 


horgan's  half-tone 


made  a  stereotype  or  electrotyped  to  get  a  printing-plate.  Our 
exhibit  is  reproduced  from  the  Photographic  Journal,  of  November 
15,  i860,  by  the  Ransom  Engraving  Company,  Ltd.,  of  Winnipeg, 
Canada. 

ROTARY  PHOTOGRAVURE. 

The  Rotary  Photogravure  Company,  of  Passaic,  New  Jersey, 
furnish  the  beautiful  insert  showing  "  A  Road  Through  the  Pines." 
The  softness  and  lack  of  mechanical  grain  of  any  kind  grows  on 
one  the  longer  the  picture  is  studied.  This  photomechanical  print- 
ing method  is  only  just  arriving  and  is  explained  for  the  first  time 
on  page  145. 

ROTARY  PHOTOGRAVURE  IN  COLORS. 

This  may  be  called  the  twentieth  century  process,  for  it  is  only 
in  its  infancy.  As  will  be  noticed  by  the  beautiful  insert,  it  retains 
all  the  character  of  the  water-color  or  pastel  original.  The  soft 
paper  on  which  it  is  printed  gives  it  an  added  charm.  The  results 
are  had  in  four  printings.  This  is  one  of  the  methods  which  prom- 
ises the  greatest  future  development.  The  Van  Dyck  Gravure 
Company,  of  New  York,  supplied  these  inserts  through  the  cour- 
tesy of  the  National  Art  Company,  also  of  New  York.  See  pages 
in  and  145  for  description  of  rotary  photogravure. 

SWELLED-GELATIN  PROCESS. 

The  splendid  results  which  John  A.  Moss  obtained  through  his 
swelled-gelatin  process  is  shown  through  an  electrotype  of  one  of 
his  plates  made  about  1876.  The  original  is  in  the  possession  of  the 
American  Typographical  Library  and  Museum,  Communipaw, 
New  Jersey.    Moss'  method  is  told  for  the  first  time  on  page  61. 

THREE-COLOR  PRINTING. 

The  success  of  the  Zeese-Wilkinson  Company,  of  New  York, 
in  three  and  four  color  reproduction  is  too  well  known  to  need 
mention  here.  Their  "  Dutch  Milkmaid "  is  a  marvelous  result  in 
three  printings.  Having  specialized  in  colorwork,  they  have  mas- 
tered its  intricacies.   Three-color  blockmaking  is  on  page  ill. 

WAVY-LINE  HALF-TONE. 

John  Swain  &  Son,  Ltd.,  contribute  a  portrait  of  Miss  Ger- 
trude Robins,  made  by  a  modification  of  the  Dargavel  wavy-line 
screen.  It  will  be  noticed  that  the  shadows  are  strengthened  by  a 
straight-line  screen  effect.  Though  the  screen  used  on  this  portrait 
is  but  sixty  lines  to  the  inch,  it  is  far  more  pleasing  than  if  made 
with  a  cross-line  screen  of  the  same  pitch. 


LEGGO  SROS.PHOTO-L1TH. 


LITHO.  BY  CHAS.  HART,  36  VESEY  ST.N.Y 


PHOTO  -  LITHO  GRAPH. 

FROM  TEXT  BOOK  ON  PLAIN  LETTERING  BY  PROF".  H.S.JACOBY. 


PHOTOLITHOGRAPHY 

APPLIED  TO 

PLANOGRAPHIC   PRINTING   FROM   ZINC,  ALUMINUM, 
STONE,  OR  THE  OFFSET  PRESS. 


Photolithography,  or  the  application  of  photography  to 
lithographic  printing,  was  the  first  of  the  photomechanical 
reproductive  processes  to  be  commercially  profitable.  It  was 
the  basis  of  a  big  business  in  New  York  when,  in  the  eighties, 
it  was  crowded  out  by  the  photorelief  processes  that  came 
into  use  at  that  time.  Had  the  offset  press  then  been  per- 
fected, photolithography  would  have  been  applied  to  the 
offset  press,  and  would  have  continued  to  be  the  most  prac- 
tical method  for  reproducing  maps,  diagrams,  charts,  cata- 
logues, and  much  of  the  illustrative  matter  of  to-day  in  which 
the  high  lights  are  desired  to  be  clear  as  in  lithography.  For 
it  must  be  remembered  that  the  principle  of  the  offset  press 
is  that  of  lithography. 

THE  OFFSET  PRESS  REVIVES  PHOTOLITHOGRAPHY. 

The  offset  press  has  revived  a  demand  for  photolithog 
raphy,  or  for  a  method  of  securing  illustrations  by  photog- 
raphy on  the  grained  zinc  plates  used  on  the  offset  press. 
Photolithography  in  the  old  days  was  practiced  in  secret,  and 
the  few  who  were  best  acquainted  with  the  methods  have 
passed  away  and  their  secret  processes  have  been  buried  with 
them. 

The  present  writer  having  been  superintendent  of  the 
largest  photolithographic  establishment  on  the  American  con- 
tinent and  having  devised  the  photolithographic  process  that 
was  used  so  successfully  there  for  about  eighteen  years  has 
been  requested  to  describe  here  for  the  first  time  the  methods 
he  used  on  the  New  York  Daily  Graphic,  the  first  illustrated 
daily  newspaper  in  the  world. 

THE  FATHERS  OF  PHOTOLITHOGRAPHY. 

It  is  of  interest  to  note  here  that  the  first  experiments  in 
photolithography  were  made  simultaneously  in  1841  by  Dixon 

11 


12 


horgan's  half-tone 


in  this  country  and  by  Lewis  in  Ireland.  Zurcher  followed 
in  1842  in  Paris.  Ten  years  later  Lemercier,  Lerebours  and 
Davanne  began  in  France  to  use  the  asphalt  process  on  stone. 
In  1855  Poitevin,  of  Paris,  patented  the  first  practical  photo- 
lithographic process.  In  1858,  Cutting  &  Bradford,  of  Bos- 
ton, patented  another  process,  and  then  came  the  most  prac- 
tical process  of  J.  W.  Osborne,  of  Melbourne,  Australia. 
The  rights  . for  the  United  States  for  Osborne's  process  were 
secured  by  the  American  Photolithographic  Company,  of 
New  York,  and  thus  began  in  the  seventies  the  use  of  photo- 
lithography for  reproducing  Government  maps,  Patent  Office 
drawings,  and  the  reproduction  of  steel  engravings  which 
were  so  popular  for  home  decoration  at  that  time. 

The  publication  of  the  first  illustrated  daily  newspaper 
in  New  York  on  March  4,  1873,  startled  the  whole  printing 
world,  for  it  demonstrated  that  photography  was  going  to 
usurp  the  place  of  wood  engraving,  which  at  that  time  was 
the  only  method  of  preparing  illustrations  for  the  printing 
press.  So  carefully  were  the  secrets  of  the  Daily  Graphic 
guarded  that  the  writer  was  under  heavy  bonds  not  to 
divulge  even  what  he  saw  in  their  extensive  photographic 
department.  In  two  years  the  writer  had  devised  a  photo- 
lithographic process  of  his  own,  which  was  the  one  afterward 
used  on  the  Daily  Graphic. 

ADVANTAGES  OF  THE  "  GRAPHIC  "  PROCESS. 

The  advantage  of  this  "  Graphic "  process,  as  it  was 
called,  was  its  simplicity,  the  great  speed  with  which  pen 
drawings  and  pencil  sketches  could  be  gotten  to  press.  No 
reversed  negative  or  routing  was  required.  No  overlaying 
or  underlaying  on  the  press,  and  still  the  daintiest  vignettes 
were  printed  with  the  softest  of  edges.  Any  number  of 
duplicate  transfers  could  be  made  for  the  many  presses 
required,  and  the  additional  feature  was  the  inexpensiveness 
of  the  process.  From  cost  records  of  a  year  on  the  Daily 
Graphic,  it  was  found  that  photolithographic  transfers, 
ready  for  transference  to  stone,  did  not  cost  a  quarter  of  a 
cent  a  square  inch. 


PHOTOLITHOGRAPHY 


13 


The  drawback  to  the  process  was  the  slowness  of  the 
lithographic  presses  of  those  days.  They  would  print  only 
about  700  to  800  an  hour.  The  Daily  Graphic  was  an  eight- 
page  paper,  the  pictorial  four  pages  were  printed  first  litho- 
graphically and  the  inside  four  pages  were  run  off  from  type 
on  a  four-cylinder  "  turtle  "  press. 

The  Daily  Graphic  newspaper  was  but  an  adve.  fcisement 
for  the  other  business,  which  included  the  Patent  Office 
Gazette;  reproductions  of  the  regular  weekly  issues  of  pat- 
ent drawings,  Government  and  real-estate  maps ;  art  repro- 
ductions ;  catalogues ;  booklets ;  cigarette  and  other  labels ; 
book  illustrations,  and  several  weekly  newspapers.  The 
quantity  of  illustrative  work  that  went  through  the  Graphic 
establishment  could  not  be  handled  by  any  of  the  photoengra- 
ving plants  of  our  day. 

And  still  the  methods  of  the  Daily  Graphic  are  entirely 
feasible  to-day,  with  the  advantage  that  through  the  use  of 
the  offset  press  they  can  be  made  more  profitable. 

REQUIREMENTS  IN  THE  PHOTOPLANOGRAPHIC  PROCESS. 

To  make  plain  the  requirements  of  the  ideal  photolitho- 
graphic —  or  as  we  have  now  changed  the  printing  surface 
from  stone  to  metal,  we  can  term  it  the  photoplanographic 
process  —  it  should  be  said  that  there  are  several  ways  of 
getting  an  image  by  photography  on  metal  ready  to  print 
from.  One  is  by  transfer,  another  by  photoengraving  intag- 
lio and  transferring  from  the  intaglio  plate,  and  lastly  photo- 
printing  direct  on  the  metal.  The  production  of  a  transfer 
direct  on  paper  by  photography  we  shall  still  call  photolithog- 
raphy and  getting  the  design  direct  on  the  metal  by  photog- 
raphy will  be  termed  photoplanography. 

THE  IDEAL  PHOTOLITHOGRAPHIC  TRANSFER. 

The  most  perfect  transfer  that  a  lithographer  handles  is 
the  one  pulled  from  an  engraving  made  for  the  purpose  on 
stone.  This  transfer  is  sharp  and  has  the  proper  amount  of 
transfer  ink,  of  the  right  consistency  to  make  the  best  possi- 
ble transfer  to  stone  or  metal  for  the  offset  press.   A  photo- 


14 


horgan's  half-tone 


lithographic  transfer  can  be  made  to  approach  this  ideal 
transfer.  The  lines  and  dots  on  it  must  be  sharp,  with  a  full 
body  of  transfer  ink  of  the  proper  degree  of  hardness.  The 
paper  support  must  be  thin,  tough,  and  have  enough  sizing  on 
it  to  prevent  the  transfer  slipping  in  transferring.  And  here 
is  where  all  the  published  methods  of  photolithography  fail, 
the  paper  coating  recommended  contains  too  soft  or  too 
heavy  a  gelatinous  coating  which  causes  the  lines  to  smash 
in  transferring. 

After  years  of  daily  experiment  with  all  the  various 
gelatins  in  the  market,  and  with  all  possible  combinations  of 
gelatin  with  albumen  and  gums  for  photolithographic  pur- 
poses, the  writer  has  found  the  following  simple  formula  to 
approach  nearest  the  ideal  method. 

THE  PAPER  TO  USE. 

The  best  paper  to  use  as  a  support  for  the  coating  on 
which  the  transfer  is  made  is  the  pure  linen  paper  known  as 
"  Saxe  "  and  "  Rives."  It  should  be  the  genuine  paper. 
There  is  an  imitation  paper  sold  under  these  names  that 
must  not  be  considered.  This  paper  comes  18  by  22  inches 
in  size  and  in  weight  about  ten  kilos  (twenty- two  pounds)  to 
the  ream.    It  should  be  coated  with  the  following  solution. 

SENSITIZING  SOLUTION  FOR  TRANSFER  PAPER. 

Nelson's  Sparkling  Gelatin   160  grams  5  ounces  69  grains 

Water   1,000  grams  zWa  ounces 

Bichromate  of  potash   100  grams  szA  ounces 

Acetic  acid,  30%  pure   50  grams  1  ounce  &/2  drams 

Chrome  alum    1  decigram  1%  grains 

The  process  is  all  very  simple  and  is  certain  of  perfect 
results,  providing  the  following  instructions  are  carried  out 
in  the  preparation  of  the  above  sensitizing  solution  and  the* 
method  of  applying  the  coating  to  the  linen  paper. 

PREPARATION  OF  THE  SENSITIZING  SOLUTION. 

Nelson's  sparkling  gelatin,  like  all  gelatins,  contains  a 
trace  of  grease,  which  must  be  removed  or  it  will  appear  as 
minute  round  bare  spots  where  the  gelatin  does  not  cover  the 


PHOTOLITHOGRAPHY 


15 


paper.  To  get  rid  of  any  possibility  of  grease  in  the  coating 
the  1 60  grams  of  gelatin  must  first  be  put  to  soak  in  the 
one  thousand  grams  of  water  until  it  has  absorbed  all  of  the 
water,  then  the  albumen  of  two  eggs  is  stirred  into  the  gela- 
tin. The  soaking  of  the  gelatin  had  better  be  done  in  one  of 
those  stoneware  breakfast-food  cookers  consisting  of  two 
vessels  fitting  one  inside  the  other.  The  lower  vessel  con- 
tains water  which  boils  over  heat,  while  in  the  upper  vessel 
is  placed  the  gelatin  to  dissolve  while  the  albumen  is  well 
stirred  in.  The  upper  vessel  is  then  covered  and  the  gelatin 
and  albumen  allowed  to  "  cook  "  for  half  an  hour,  or  until 
the  albumen  appears  to  be  coagulated  and  is  floating  with 
other  foreign  matter  on  the  surface  of  the  heated  gelatin. 
Strain  the  gelatin  while  hot  through  a  muslin  bag  into  a 
glazed  pitcher  or  an  enameled-ware  vessel. 


SIMPLE   APPARATUS   FOR   COATING  PAPER. 


Gelatin  is  exceedingly  sensitive  to  chrome  alum.  The 
slightest  trace  of  the  alum  has  a  hardening  effect  on  it,  to  a 
degree,  so  that  it  is  necessary  to  add  the  alum  to  the  bichro- 
mate of  potash  and  grind  both  in  a  mortar  to  a  fine  powder, 
and  then  while  stirring  the  hot  gelatin  pour  in  the  bichromate 
powder  slowly.  The  acetic  acid  can  then  be  added  and  the 
whole  filtered  again. 

The  first  method  I  employed  for  coating  the  paper 
required  two  pairs  of  hands.  One  pair  of  hands  to  pull  the 
paper  through  the  "  guard  "  and  the  other  pair  to  lower  the 


16 


horgan's  half-tone 


"  guard  "  to  just  the  right  depth  on  the  surface  of  the  gelatin. 
The  tin  trough  to  hold  the  gelatin  and  the  construction  of 
the  "  guard  "  are  shown  in  the  diagram. 

The  "  guard  "  is  made  of  well-seasoned  hardwood,  with 
a  piece  of  No.  8  brass  wire  secured  to  it  with  two  screws  at 
both  sides.  The  wire  guides  the  sheet  of  paper  to  the  edge 
of  the  scraper  so  that  the  paper  does  not  go  below  the  surface 
of  the  solution  and  permit  any  of  it  to  flow  on  the  back  of  the 
paper.  Of  course  the  "guard"  can  be  lowered  so  that  the 
solution  may  flow  over  the  back,  but  the  object  of  the 
"  guard  "  is  to  prevent  this,  and  a  little  practice  will  teach 
just  how  to  do  the  coating  properly. 


ONE-MAN  DEVICE  FOR  COATING  PAPER. 


After  a  few  months'  use  of  the  "  guard  "  guided  by  hand 
1  devised  a  simpler  and  better  method  of  coating  the  paper 
which  was  used  ever  after. 

This  most  effective  device  was  made  by  fastening  the 
"  guard  "  to  two  pieces  of  tongued  strips  that  fitted  into  and 
moved  up  and  down  in  grooved  strips.  The  "  guard  "  thus 
became  part  of  a  square  frame.  Two  springs  held  the  guard 


PHOTOLITHOGRAPHY 


17 


suspended  so  that  the  "  guard  "  was  above  the  trough.  A 
foot-pedal,  connected  with  this  frame  and  guard  by  an  iron 
rod,  brought  down  the  frame  by  pressure  of  the  foot  on  the 
pedal  so  that  a  single  operator  could  pull  the  sheet  through 
with  his  hands  while  he  regulated  the  contact  of  the  sheet 
with  the  solution  by  the  pedal.  As  the  surface  of  the  gelatin 
coating  solution  lowers  in  the  trough  a  thumbscrew  regu- 
lates the  frame  so  that  the  proper  distance  of  the  "  guard  " 
from  the  solution  is  maintained.  Just  over  the  trough  was 
fixed  a  bar  through  which  two  pin-points  projected.  On 
these  points  the  sheet  was  hung  to  drain  in  the  trough  while 
the  sheet  was  examined  for  air-bells  and  specks  of  dirt. 
The  diagram  shows  the  device. 

DRYING  THE  COATED  SHEETS. 

After  the  sheets  are  coated  they  are  not  pinned  up  but 
hung  on  pin-points  in  this  way:  Square  wooden  rods,  2 
inches  square  and  8  feet  long,  are  punctured  through,  near 
one  edge,  with  large  "  bank  "  pins  so  that  the  points  project 
through,  and  the  corners  of  the  paper  are  hooked  on  these 
pin-points;  the  points  being  arranged  about  twenty  inches 
apart  so  that  they  come  near  the  corners  of  a  22-inch  wide 
sheet  of  paper.  When  one  of  these  racks  is  filled  with  the 
five  sheets  which  it  will  hold,  it  is  removed  so  that  another 
rack  may  be  filled.  Of  course  these  plans  are  for  a  large 
establishment,  for  the  writer  was  accustomed  to  coating 
from  thirty  to  eighty  sheets  a  day.  The  methods  for  a 
smaller  plant  will  be  described  later. 

THE  COATING-ROOM. 

The  darkroom  in  which  the  coating  and  drying  of  this 
sensitized  transfer  paper  is  done  should  be  heated  with 
steam-pipes  so  arranged  that  a  temperature  of  from  8o°  to 
1 300  F.  may  be  had  any  day  in  the  year.  Further,  an  outlet 
valve  must  be  placed  on  the  steam-pipes  so  that  "  live  "  steam 
may  be  turned  on  in  the  coating-room.  A  wet  and  dry  bulb 
thermometer  or  psychrometer  will  give  the  degrees  of  heat 
and  humidity.  While  the  paper  is  being  coated  the  dry  ther- 

2 


IS 


horgan's  half-tone 


mometer  should  record  8o°  F.  and  the  wet  bulb  thermometer 
ten  degrees  lower.  After  the  coating  is  finished  heat  may  be 
turned  on  in  the  room  until  it  reaches  1300  F.  without  injury 
to  the  paper.  In  fact  the  quicker  it  dries,  within  certain 
limits,  the  higher  the  gloss  on  the  paper  and  the  sharper  the 
line  that  can  be  developed  on  it  later.  The  moisture  in  the 
room  allows  the  hot  gelatin  to  take  hold  of  the  fiber  of  the 
paper  by  penetrating  its  surface  before  drying,  and  also  keeps 
the  paper  from  curling  at  the  bottom  when  drying. 

INSTRUCTIONS  FOR  COATING  PAPER. 

The  principal  points  to  be  observed  in  the  coating  of  the 
paper :  When  pulling  the  sheet  through  the  "  guard  "  it  will 
be  found  that  the  quicker  the  sheet  is  drawn  through,  the 
heavier  the  coating  raised  from  the  trough  on  the  surface  of 
the  paper;  while  the  slower  the  paper  is  drawn  over  the 
solution,  the  thinner  the  coating  left  on  the  paper.  By  taking 
advantage  of  these  points  a  perfectly  even  coating  may  be 
had  on  the  paper.  If  the  sheet  is  started  through  the 
"  guard  "  quickly  and  the  speed  gradually  slackened  as  the 
end  of  the  sheet  is  being  coated,  then  the  coating  will  be  even 
as  regards  the  top  and  the  bottom  of  the  sheet.  The  reason 
for  this  being  that  with  a  heavier  coating  on  the  top  of  the 
sheet  and  a  thinner  coating  below,  the  whole  equalizes  before 
the  gelatin  sets.  The  precise  speed  for  pulling  the  sheet 
through  can  only  be  learned  by  practice.  Another  point  to 
be  guarded  against  is  air-bells  on  the  surface  of  the  sheet. 
These  must  be  watched  for  and  touched  with  the  end  of  the 
finger  while  the  solution  is  still  flowing  so  that  the  bare  spot 
is  covered  and  will  not  show  when  the  coating  is  dry.  The 
third  danger  to  avoid  is  that  the  bottom  corners  of  the  sheet 
do  not  curl  so  as  to  stick  to  the  face  of  the  paper.  The 
bottom  edge  of  the  paper  has  a  tendency  to  curl  inward, 
though  only  for  a  minute  or  so,  when  it  straightens  out  again 
and  will  dry  almost  straight  in  a  hot,  humid  room.  It  is 
needless  to  add  that  the  coating-room  should  be  lit  by  a  yel- 
low light,  as  the  paper  when  dry  is  quite  sensitive  to  actinic 
light.  An  electric  incandescent  bulb  will  not  injure  the  paper. 


PHOTOLITHOGRAPHY 


19 


Within  an  hour  or  less  time  the  paper  should  be  thor- 
oughly dry.  After  taking  it  down,  the  strip  at  the  bottom 
of  each  sheet  containing  a  thick  rim  of  gelatin  should  be 
sheared  off  and  the  paper  stored  in  a  pile  with  a  weight  on 
it  to  keep  the  sheets  flat.  A  portfolio  with  covers  of  heavy 
wooden  boards  makes  a  good  holder  to  keep  ,  the  sensitized 
sheets  perfectly  flat.  The  printing-room  where  the  sensi- 
tized transfer  paper  is  used  should  of  course  be  lighted  only 
by  yellow  light.  Any  quantity  of  light  may  be  allowed  into 
the  printing-room  provided  the  light  is  entirely  yellow. 

THE  NEGATIVE  REQUIRED  FOR  PLANOGRAPHIC  PRINTING. 

One  great  advantage  the  photoplanographic  transfer 
method  has  over  the  photorelief  plate  methods  is  that  the 
negative  required  for  the  former  does  not  require  the  inten- 
sity necessary  for  the  latter.  Therefore  the  greater  grada- 
tions in  the  lines  and  dots  can  be  had  by  the  transfer  method. 
Every  experienced  photographer  understands  the  great  loss 
in  gradations  in  a  negative  when  intensification  has  to  be 
forced.  And  the  destructive  action  of  the  "  cutting  "  solu- 
tion when  clearing  the  deposit  from  filled-in  fine  lines  is 
known  to  every  one  who  thoroughly  understands  making  a 
process  negative.  So  that  the  transfer  method  has  in  its 
favor  the  possibility  of  starting  with  a  perfect  negative,  and 
a  perfect  negative  should  precede  the  manipulations  of  all 
photo  processes,  though  unfortunately  that  is  not  always  so. 

THE  COLLODION. 

The  simplest  way  to  keep  a  formula  for  collodion  in  mind 
is  to  know  the  number  of  grains  of  each  ingredient  used  to 
each  ounce  of  the  solution,  which  is  ether  and  alcohol  com- 
bined. It  is  important  that  the  chemicals  used  should  be 
pure.  The  alcohol  should  be  ninety-five  per  cent  grain  alco- 
hol. If  it  contains  much  more  water  than  five  per  cent  it 
will  not  dissolve  the  guncotton  perfectly.  The  ether  should 
be  that  known  as  sulphuric  ether,  though  much  of  the  collo- 
dion base  sold  is  made  with  methylated  ether.  The  pyroxylin, 
commonly  known  as  guncotton,  is  most  important.  There 


20 


horgan's  half-tone 


are  some  brands  to  be  found  that  are  excellent,  though  gun- 
cotton  is  exceedingly  variable  in  its  character.  It  pays  to 
buy  a  good  make  of  guncotton,  and  if  it  works  well  continue 
using  that  brand.  The  iodid  of  ammonium  can  be  purchased 
with  crystals  either  white  or  brown  in  color.  The  writer, 
using  large  quantities  of  collodion,  prefers  the  brown 
because  collodion  made  with  it  "  ripens  "  quickly  and  gives 
greater  intensity  in  the  negative,  though  it  does  not  keep  in 
condition  for  use  so  long  as  collodion  made  with  the  white 
crystals.  The  bromid  of  cadmium  is  the  preservative  in  the 
collodion.  Remember  always  that  iodids  in  a  collodion  give 
hardness  or  contrast  —  just  what  is  required  in  line  negative- 
making  —  and  the  bromids  produce  softness. 

FORMULA  FOR  LINE  COLLODION. 

Here  is  the  simplest  formula  for  collodion  ever  published. 
It  is  the  result  of  years  of  practical  experiment,  and,  when 
tried,  will  be  found  to  give  superior  results,  with  the  further 
advantage  that  it  does  not  contaminate  the  silver  bath  as 
quickly  as  the  complicated  formulas  for  collodion  that  are 
in  common  use.  This  collodion  is  ready  for  use  almost  imme- 
diately after  compounding. 

Alcohol  and  ether  Equal  parts 

Guncotton.  .7  grains  to  the  ounce  of  combined  alcohol  and  ether 

Iodid  of  ammonium  5  grains  to  the  ounce  of  above 

Bromid  of  cadmium  1  grain  to  the  ounce  of  above 

The  amount  of  guncotton  can  be  varied  to  suit  the  char- 
acter of  the  cotton,  and  the  size  of  the  glass  to  be  flowed 
with  the  collodion.  It  will  be  understood  that  small-sized 
pieces  of  glass  can  be  covered  with  collodion  quickly  and 
consequently  a  thicker  solution  can  be  used,  while  with  large 
sheets  of  glass  the  coating  of  the  surface  with  collodion  takes 
so  much  longer  that  the  greater  evaporation  of  the  ether  and 
alcohol  produces  a  thicker  film  from  a  thin  solution  than 
when  small  sheets  of  glass  are  coated.  Where  the  average- 
sized  sheets  of  glass  to  be  coated  are  14  by  17  inches,  then 
five  grains  of  guncotton  to  the  ounce  might  be  sufficient. 


PHOTOLITHOGRAPHY 


21 


The  writer  used  when  coating  the  larger  sizes  of  glass  up  to 
22  by  26  inches  a  glass  plate  rest,  as  shown,  and  always 
drained  the  collodion  into  a  funnel  set  into  a  table.  In  the 
bottom  of  the  funnel  was  a  pledget  of  cotton  through  which 
the  collodion  was  filtered  into  a  bottle  under  the  table. 


The  glass  used  for  negative-making  should  of  course  be 
perfectly  clean  and  be  coated  on  one  side  with  a  substratum 
of  albumen  to  keep  the  collodion  film  secure  to  the  glass 
support  during  all  the  washing  operations. 

TO  CLEAN  GLASS. 

Nitric  acid  and  water  will  answer  for  cleaning  glass. 
A  solution  of  1  part  nitric  acid  in  10  parts  of  water,  kept  in 
a  stoneware  tank,  makes  a  good  glass-cleaning  solution.  The 
glass  should  be  left  in  this  cleansing  bath  over  night.  It 
would  be  better  to  stand  the  sheets  of  glass  on  their  edges 
if  the  bath  is  deep  enough.  If  the  glass  plates  must  be  laid 
flat  on  each  other  it  would  be  well  to  have  some  short  pieces 


22 


horgan's  half-tone 


of  straw  to  go  between  the  sheets  to  keep  them  separated  so 
that  the  acid  solution  may  attack  the  whole  surface  of  the 
glass.  Straw  is  not  readily  acted  upon  by  nitric  acid,  and  it 
does  not  injure  the  surface  of  the  glass. 

In  the  morning  the  glass  should  be  removed,  without 
scratching,  from  the  acid  bath.  When  it  is  drained  each 
sheet  should  be  laid  on  a  broad  clean  board  and  scrubbed 
with  a  bristle  brush  on  both  sides  and  particularly  on  the 
edges.  These  edges  are  too  often  neglected,  and  the  dirt 
from  them  is  one  of  the  causes  of  contamination  of  the  silver 
bath.  When  the  dirt  is  scrubbed  completely  from  the  glass 
it  is  washed  on  both  sides  under  the  running  water  from  a 
tap,  drained,  and  flowed  with  the  following  substratum. 

ALBUMEN  SUBSTRATUM  FOR  GLASS. 

The  albumen  from  one  fresh  egg,  which  should  weigh 
about  an  ounce,  is  beaten  up  thoroughly  and  mixed  with 
forty  ounces  of  clean  water,  after  which  a  dram  of  water 
ammonia,  stronger,  U.  S.  P.  twenty-six  per  cent,  is  added. 
This  solution  is  filtered  carefully  and  flowed  on  one  side  of 
the  glass  only,  then  the  glass  is  stood  up  on  its  edge  in  a  rack 
to  dry  in  a  place  free  from  dust.  The  proper  cleaning  and 
albumenizing  of  the  glass  assures  success  in  the  subsequent 
operations  of  negative-making  so  far  as  preventing  dirt  from 
appearing  under  the  film  on  development  or  permitting  the 
collodion  to  tear  and  strip  from  the  glass  during  the  wash- 
ing operations.  This  work  should  not  be  left  to  a  careless 
boy,  without  being  supervised  occasionally  to  see  that  it  is 
properly  done. 

THE  SILVER  BATH. 

The  preparation  of  the  silver  bath  is  the  simplest  of 
operations,  though  it  is  the  solution  that  gives  the  most 
trouble  owing  to  the  principles  governing  its  proper  working 
not  being  understood. 

Distilled  water  containing  forty  to  forty-five  grains  of 
nitrate  of  silver  to  each  ounce  of  water,  made  slightly  acid 
with  a  few  drops  of  chemically  pure  nitric  acid  and  contain- 


PHOTOLITHOGRAPHY 


23 


ing  a  trace  of  iodin,  is  all  that  constitutes  a  perfect  silver 
bath. 

The  trouble  comes  from  the  fact  that  the  proportions  of 
the  ingredients  begin  to  change  from  the  sensitizing  of  the 
first  plate  in  the  silver  bath,  and  besides,  foreign  matter  is 
absorbed  by  it. 

Sufficient  silver-bath  solution  should  always  be  on  hand 
to  fill  twice  the  holder  or  dish  in  which  the  silver  bath  is  used. 
When  the  quantity  of  distilled  water  required  is  measured, 
then  forty  grains  of  nitrate  of  silver  is  dissolved  in  the  water 
and  the  solution  tested  for  acidity  with  litmus  paper.  Nitric 
acid,  chemically  pure,  is  added  drop  by  drop  and  stirred  in 
until  the  solution  just  turns  acid.  A  glass  plate  is  coated 
with  collodion  and  lowered  on  a  holder  into  the  silver  bath. 
This  collodionized  plate  is  left  in  the  bath  for  say  fifteen 
minutes,  when  the  solution  will  have  absorbed  enough  iodin 
from  the  collodion  to  put  the  bath  in  proper  condition. 

Should  the  first  plate  sensitized  in  the  new  silver  bath 
show  a  slight  fog  over  the  whole  plate  —  a  fog  that  can  be 
removed  by  the  finger  from  the  surface  —  then  the  silver 
bath  requires  a  few  more  drops  of  nitric  acid.  If  the  first 
negative  is  thin  in  appearance,  then  the  amount  of  iodid  in 
the  bath  is  still  insufficient.  This  last  will  remedy  itself  after 
a  few  plates  are  sensitized  in  it. 

About  all  that  is  necessary  to  be  borne  in  mind  regarding 
the  silver  bath  is  :  Each  plate  sensitized  in  it  removes  some  of 
the  nitrate  of  silver  and  adds  a  little  alcohol,  ether,  iodid  of 
ammonium  and  particles  of  dirt.  The  dirt  can  be  filtered  out, 
if  the  bath  is  not  so  acid  that  it  dissolves  the  dirt.  The  alco- 
hol and  ether  can  be  evaporated  out.  The  iodids  can  be 
removed  by  pouring  the  silver  bath  into  a  quantity  of  dis- 
tilled water,  when  the  iodid  will  be  changed  from  solution 
into  fine  particles  in  suspension,  shown  by  the  bath  turning  a 
creamy  white.  These  iodid  particles  can  then  be  filtered  out 
and  the  bath  strengthened  up  to  the  normal  forty  grains  to 
the  ounce;  or,  the  bath  can  be  placed  in  a  porcelain  evapo- 
rating-dish  and  the  excess  of  water,  together  with  the  alcohol 
and  ether,  evaporated  until  the  bath  is  reduced  to  its  original 


24 


horgan's  half-tone 


bulk.  During  warm  weather  the  exposure  to  the  sun  for 
days  of  the  bath  solution  not  in  use,  in  a  white  glass  bottle, 
is  often  sufficient  to  evaporate  the  alcohol  and  ether  in  it  and 
throw  down  to  the  bottom  the  dirt  and  other  foreign  matter 
from  the  solution. 

THE  CAMERA  AND  LENS. 

The  offset  press  can  print  maps  so  much  larger  than  the 
typographic  press  that  it  would  seem  as  if  the  cameras  used 
for  offset-press  work  would  have  to  be  so  much  larger,  which 
is  not  the  case.  The  photoplanographic  process  here  de- 
scribed permits  the  making  of  the  largest  maps  in  several 
sectional  negatives  which  may  afterward  be  printed  on  trans- 
fer paper,  and  the  transfers  joined  together  perfectly  so  that 
the  necessity  of  large  negatives  is  obviated. 

A  camera  to  make  a  negative  14  by  17  inches  and  smaller 
is  the  size  of  camera  most  serviceable.  It  should  be  strongly 
built  and  used  on  a  camera  stand  of  the  most  rigid  pattern. 
The  bed  of  the  camera-stand,  or  the  whole  camera-stand, 
should  be  supported  on  springs  of  some  kind  to  absorb  the 
vibration,  for  vibration  is  the  greatest  enemy  of  sharp  nega- 
tives. Do  not  rest  the  camera  on  the  floor  and  fasten  copy  to 
the  wall  in  the  expectation  of  getting  perfectly  sharp  nega- 
tives. 

For  a  lens  choose  one  of  the  anastigmats  of  modern  con- 
struction, and  have  its  focal  length  about  that  of  the  diagonal 
of  the  largest  plate  to  be  made  with  it.  For  instance,  the 
size  of  the  actual  work  on  a  14  by  17  negative,  allowing  one- 
half  inch  margin  all  around  for  working,  is  13  by  16  inches. 
The  diagonal  of  this  is  20^  inches,  therefore  a  lens  of 
twenty  inches  focal  length  would  be  ample.  It  will  be  found 
that  with  some  of  the  modern  lenses  a  sixteen-inch  focus  lens 
will  cover  sharply  a  14  by  17  plate  by  using  a  small  dia- 
phragm, which  lengthens  the  time  of  exposure.  Where  much 
small  work  is  done  on  say  8  by  10  inch  glass,  then  an  addi- 
tional lens  of  about  ten  inches  focus  is  a  great  saver  of  time 
and  money. 

An  exceedingly  fine-grained  ground  glass  is  essential  for 


PHOTOLITHOGRAPHY 


25 


sharp  focusing  together  with  a  strong  magnifying  focusing 
glass. 

REVERSED  NEGATIVES. 

The  offset  press  requires  reversed  transfers  so  that  nega- 
tives for  it  should  be  reversed  as  regards  right  and  left.  This 
can  be  done  through  the  use  of  a  prism  or  mirror  in  connec- 
tion with  the  lens,  or  by  stripping  the  negative  film  from  its 
glass  support  and  turning  it  over  as  is  done  in  photoengra- 
ving. There  is  the  third  method  of  reversing,  which  consists 
in  turning  the  glass,  instead  of  the  film  side,  toward  the  lens, 
thus  photographing  through  the  glass.  All  three  methods 
are  in  use. 

Reversal  through  the  prism  is  the  most  reliable  way, 
though  it  increases  the  time  for  exposing  the  negative  at 
least  twice  and  frequently  three  times.  The  camera  must  be 
arranged  at  right  angles  with  the  copy-board  when  a  prism 
is  used.  Mirrors  can  be  had  as  substitutes  for  the  prism. 
These  are  made  either  of  optically  flat  glass  silvered  on  its 
surface  or  of  polished  speculum  metal.  Mirrors  are  less 
costly  than  prisms  to  begin  with,  but  after  use  they  are  liable 
to  be  scratched  in  the  frequent  polishing  necessary  when  they 
do  not  reflect  the  image  sharply,  so  a  prism  is  the  cheaper 
investment. 

Stripping  the  negative  film  and  turning  it  over  on  the 
glass  support  is  adequately  described  in  the  chapter  on  photo- 
engraving. A  drawback  to  this  method  of  reversal  is  the 
danger  of  distortion  in  the  design  when  several  films  are  to 
be  joined  to  make  up  a  large  design,  or  lack  of  register  when 
making  separate  color-plates  in  a  color-plate  set.  When 
slight  distortion  does  not  matter,  reversal  by  turning  the 
negative  is  a  quite  practical  method. 

Reversal  by  turning  the  glass  side  of  the  sensitized  plate 
toward  the  lens  instead  of  the  film  side,  as  is  customary,  is 
an  effective  method  providing  good-quality  glass  is  used  and 
the  back  of  the  glass,  which  is  to  face  the  lens,  is  polished 
perfectly  clean  before  inserting  in  the  plateholder.  When 
developing  a  plate  exposed  this  way  it  must  be  remembered 
that  the  image  will  appear  on  the  under  side  of  the  film. 


26 


horgan's  half-tone 


The  uprights  supporting  the  copy-board  should  be  abso- 
lutely rigid  so  as  to  prevent  the  slightest  possibility  of  vibra- 
tion. The  copy-board  itself  must  be  at  right  angles  in  every 
direction  with  the  axis  of  the  lens.  That  is,  it  must  be  par- 
allel with  the  ground  glass  and  sensitive  plate,  and  when  a 
prism  or  mirror  is  used  the  copy-board  must  be  at  absolute 
right  angles  with  the  sensitive  plate.  This  is  in  order  that 
there  shall  be  no  distortion  in  the  dimensions  of  the  image 
on  the  ground  glass. 

The  copy-board  itself  should  slide  in  grooves  laterally  so 
that  it  may  be  taken  out  if  necessary  and  laid  down  on  a 
table  when  intricate  copy  is  to  be  attached  to  it.  Another 
reason  for  the  lateral  movement  is  that  when  a  prism  or 
mirror  is  used,  the  copy-board  will  have  to  be  pushed  to  one 
side  of  its  normal  center. 

Copy-boards  crossed  with  grooves  or  bored  with  holes  in 
which  clips  are  used  to  hold  down  the  copy  are  most  excel- 
lent ideas.  Another  plan,  to  secure  copy  flat  without  punc- 
turing it  with  holes  from  tacks  or  pins,  is  a  glass  frame,  on 
the  photographic  printing-frame  principle,  and  called  a 
"  copy-holder,"  in  which  the  copy  is  first  framed  and  then 
the  frame  itself  secured  to  the  copy-board.  A  large  sheet  of 
plate  glass  can  be  used  to  hold  copy  flat  and  the  plate  glass 
held  by  clamps  to  the  copy-board,  though  by  this  plan  there 
is  danger  of  reflection  of  light  from  the  camera  and  its  sur- 
roundings into  the  lens. 

Reflected  light  in  the  lens  other  than  that  from  the  copy 
will  give  the  photographer  constant  trouble  if  he  does  not 
watch  out  for  it. 

All  copy-boards  should  be  painted  a  dull  black.  The 
reason  for  it  is  this :  All  extra  light  reaching  the  sensitive 
plate  other  than  that  coming  from  the  copy  uses  up  both 
silver  and  developer  that  should  go  to  building  up  the  intense 
image  on  the  photographic  plate.  It  would  seem  but  a  small 
matter,  still  it  is  the  cause  of  thousands  of  dollars  waste  each 
year,  and  this  is  the  first  time  that  attention  has  been  called 
to  it. 

For  even  illumination  of  large-sized  copy  there  is  nothing 


PHOTOLITHOGRAPHY 


27 


to  compare  with  daylight.  As  this  light  must  come  through 
glass,  there  should  be  ample  skylight  and  side  lights  when 
possible.  The  writer  always  used  a  plate-glass  mirror  as 
wide  as  the  copy-board  to  rest  on  the  camera  bed  and  reflect 
the  light  from  above  toward  the  copy.  This  mirror  will  be 
found  indispensable,  once  used.  It  is  well  to  have  the  front 
of  the  camera  cone-shaped,  that  is  that  the  front  holding  the 
lens  should  be  as  small  as  possible,  so  that  it  does  not  cut  off 
too  much  light  when  enlarging  copy.  The  drawback  to  day- 
light is  that  it  changes  as  the  day  progresses,  or  when  the 
sky  is  overcast  with  clouds  so  that  proper  calculation  of 
exposures  to  meet  changing  conditions  is  difficult. 

On  the  Daily  Graphic  the  writer  had  the  immense  sky- 
light room  on  the  roof  connected  with  the  darkrooms  below 
with  an  elevator.  The  operators  in  the  "  lightroom,"  as  it 
was  called,  looked  after  the  focusing  of  copy  and  the  expo- 
sure of  the  sensitive  plates  so  that  they  became  expert  in 
noting  changes  in  the  light  and  making  calculations  therefor. 
The  men  in  the  darkroom  below  never  did  anything  but  the 
development  and  intensifying  of  the  negatives.  This  division 
of  the  work  is  much  better  in  large  establishments  than 
where  each  operator  has  to  work  in  both  lightroom  and  dark- 
room alternately.  The  constant  changing  from  lightroom  to 
darkroom  is  injurious  to  the  eyes,  and  while  he  is  working 
in  the  darkroom  the  camera  is  idle  and  while  using  the  camera 
the  darkroom  is  unoccupied. 

ELECTRIC  LIGHTING. 

There  is  economy  in  the  electric  lighting  of  copy  on 
account  of  the  uniformity  of  the  illumination,  though  it  can 
not  compare  with  daylight  in  the  evenness  of  illumination. 
Through  the  use  of  electric  lights  the  calculation  of  exposure 
should  be  the  same,  morning,  noon  or  night,  winter  or  sum- 
mer, so  that  the  output  of  negatives  can  be  calculated  upon 
to  a  certainty,  and  this  is  the  only  way  to  make  the  business 
profitable. 

Improvements  are  coming  so  frequently  in  electric  light- 
ing that  what  could  be  stated  here  as  to  the  best  type  of 


28 


horgan's  half-tone 


electric  lamp  to  use  might  become  in  a  few  months  out  of 
date.  In  the  early  days  we  had  the  open-arc  type  of  lamp, 
supplied  from  our  own  dynamo  as  the  street  service  current 
was  unreliable;  then,  after  various  changes  in  the  types  of 
lamps,  we  thought  the  question  was  solved  with  the  Cooper- 
Hewitt  light.  Then  came  the  enclosed  arc  lamp  as  an 
improvement,  and  now  the  flaming  arc  type  of  lamp  is  pre- 
ferred. 

For  economy  of  current  and  the  photographing  of  black 
and  white  copy  the  enclosed  type  of  arc  lamp  is  still  used ; 
while  for  copy  in  colors  or  where  speed  is  necessary  in  turn- 
ing out  work,  the  flaming  arc  type  of  lamps,  notwithstanding 
their  increased  consumption  of  current,  are  after  all  the  more 
economical.  The  most  perfect  method  of  artificially  illumi- 
nating copy  has  not  yet  been  devised.  In  the  crowded  con- 
ditions that  usually  prevail  around  copying  cameras  it  is 
better  to  have  the  electric  arc  lamps  suspended  from  over- 
head trolleys  so  they  can  be  moved  near  or  far  from  the 
copy-board,  and  the  lamps  should  be  counterbalanced  by 
weights  or  other  device  so  that  they  can  be  raised  and  lowered 
with  ease. 

MAKING  THE  NEGATIVE. 

These  instructions  refer  particularly  to  the  application  of 
photography  to  reproduction  for  planographic  printing  either 
from  stone  or  metal  plates  on  the  lithographic  press  or  from 
the  offset  press.  In  this  work  large-sized  pieces  of  copy  must 
be  considered,  and  large  negatives  must  be  handled.  So  we 
will  begin  by  fastening  the  copy  to  the  copy-board  before 
sensitizing  the  plate,  for  the  reason  that  if  there  is  any 
contraction  or  expansion  to  take  place  in  the  copy  due  to 
atmospheric  changes  these  movements  will  occur  before  the 
exposure. 

CARE  OF  THE  COPY. 

No  matter  what  the  method  or  combination  of  methods 
used  in  attaching  the  copy  to  the  board,  the  habit  should  be 
acquired  at  the  beginning  of  treating  each  piece  of  copy  as  if 
it  was  as  precious  as  the  original  Declaration  of  Indepen- 


PHOTOLITHOGRAPHY 


29 


dence.  Clean  hands  and  clean  tables  —  everything  clean 
which  the  copy  may  touch.  But  above  all  things  do  not  use 
carpet-tacks  or  nails  to  punch  holes  in  the  copy  when  fasten- 
ing it  to  the  board.  Use  glass  push-pins  with  steel  points 
and  large  bank-pins,  if  tacks  of  some  kind  must  be  used,  as 
these  do  not  puncture  large  holes  in  copy  and  are  most  effect- 
ive in  holding  to  the  soft  pine  wood  of  the  copy-board.  The 
bank-pins  are  ordinary  pins  about  three  inches  in  length. 
Whenever  possible,  a  large  sheet  of  polished  plate  glass 
should  be  utilized  to  press  copy  flat  to  the  board,  taking  care 
that  reflections,  even  that  of  the  lens  in  the  plate  glass,  are 
watched  out  for  and  provided  against. 

FOCUSING. 

The  ground  glass  on  which  the  focusing  is  done  is  sup- 
posed to  be  of  the  very  finest  grain,  still  it  is  well  to  paint 
two  streaks  of  glycerin  or  oil  across  the  ground  glass  from 
corner  to  corner  so  that  even  finer  focusing  may  be  done. 
Parallelism  between  the  ground  glass  and  copy-board  is 
absolutely  essential,  particularly  when  several  negatives 
must  be  made  from  different  sections  of  large  copy,  to  be 
joined  together  later.  Measurement  on  the  ground  glass  of 
a  large  square  on  the  copy-board  is  one  way  of  determining 
this  perfect  parallelism,  though  other  methods  will  suggest 
themselves  to  the  intelligent  operator.  With  most  lenses  it 
is  best  to  focus  sharp  with  a  large  diaphragm  midway 
between  the  center  and  the  corner  of  the  copy,  and  then  trust 
to  the  smaller  diaphragm,  used  when  exposing  the  plate  to 
bring  all  of  the  copy  sharp  on  the  plate.  It  is  while  focusing 
that  reflections  of  stray  light  should  be  looked  out  for. 
When  illuminating  large  drawings,  particularly  on  tracing- 
cloth,  where  the  India  ink  is  glossy,  there  is  a  danger  of 
reflected  light  from  the  glossy  ink  at  the  edges  of  the 
drawing. 

These  instructions  are  intended  for  the  photographer 
who  has  had  experience  in  the  manipulations  of  the  wet 
plate,  so  that  the  details  regarding  collodionizing,  etc.,  will 


30 


horgan's  half-tone 


not  be  gone  into  except  where  they  relate  to  handling  the 
large  work  required  by  the  planographic  press. 

COLLODIONIZING,  SENSITIZING  AND  EXPOSING  THE  PLATE. 

The  plate  rest  recommended  when  collodionizing  large 
plates  shown  in  the  paragraph  on  collodion  will  be  found 
essential.  The  regular  collodion  bottles  with  glass  covers 
prevent  dust  and  the  evaporation  of  the  solvents  and  are 
indispensable.  For  sensitizing  the  plates  an  upright  dipping 
bath  for  plates  up  to  twenty  inches  is  most  convenient,  but 
when  plates  are  larger  one  way  than  twenty  inches  a  tilting 
flat  dish  is  preferable. 

Care  in  dipping  plates  into  the  upright  bath  or  flowing 
them  with  the  silver  solution  when  a  tray  is  used  to  prevent 
streaks  is  well  known.  After  the  plate  is  sensitized  it  should 
be  slowly  raised  from  the  silver  bath  and  hung  on  the  dipper 
over  the  bath  so  as  to  drain  as  much  of  the  silver  solution  as 
possible  back  into  the  bathholder.  When  thoroughly  drained 
the  glass  plate  is  allowed  to  rest  on  strips  of  clean  blotter, 
while  the  top  edge  of  the  plate  and  the  back  are  wiped  dry 
of  silver  solution. 

If  the  exposure  is  to  be  prolonged  and  there  is  danger  of 
the  plate  drying,  a  sheet  of  black  or  red  blotter  wet  with 
water  is  laid  on  the  back  of  the  plate.  With  the  method  of 
exposure  the  operator  is  supposed  to  be  familiar.  As  to  the 
time  of  exposure,  that  is  a  matter  impossible  to  advise  on,  as 
it  varies  with  every  factor  that  goes  into  the  making  of  the 
negative. 

DEVELOPMENT. 

It  is  in  the  development  of  large  negatives  that  the  skill 
of  the  operator  is  most  evident.  But  we  will  first  consider 
the  composition  of  the  developer.  It  is  well  to  fix  in  the 
mind  that  the  amount  of  iron  sulphate,  U.  S.  P.,  need  not  be 
greater  than  eighteen  grains  to  the  ounce  of  water.  In  the 
early  developers  we  used  it  was  as  high  as  thirty  grains  to 
the  ounce  of  water.  Iron  is  the  developing  agent,  acetic  acid 
being  added  to  restrain  the  action  of  the  iron  and  prevent 


PHOTOLITHOGRAPHY 


31 


fogging,  while  alcohol  is  added  merely  to  make  the  developer 
flow  readily  when  the  silver  bath  contains  an  excess  of  alco- 
hol. These  are  the  principles  that  govern  this  most  impor- 
tant operation  and  now  are  the  approved  practice. 

Iron  sulphate,  U.  S.  P.,  in  pure  crystals  should  be  put,  on 
receipt,  into  a  stoneware  crock  and  covered  with  clean  or 
distilled  water  until  a  saturated  solution  of  iron  is  formed. 
For  use  take  some  of  this  saturated  solution  and  dilute  it 
with  clean  water  until  it  tests  twenty  degrees  with  a  regular 
water  hydrometer.  (Such  as  is  used  for  testing  silver  baths.) 
To  every  twenty-four  ounces  of  this  iron  solution  add  one 
ounce  of  thirty  per  cent  pure  acetic  acid  or  one-half  ounce  of 
glacial  acetic  acid.  Enough  grain  alcohol  —  not  wood  alco- 
hol —  may  be  then  added  to  make  the  developer  flow  readily. 
With  a  new  bath  no  alcohol  should  be  required. 

THE  ADDITION  OF  GELATIN  TO  DEVELOPER. 

The  writer  has  experimented  with  the  addition  of  sugar, 
molasses  and  other  colloidal  substances  to  the  developer  and 
finally  settled  on  the  following  as  being  the  best  restrainer 
for  developing  large  plates. 

An  ounce  of  gelatin  is  allowed  to  soak  up  as  much  cold 
water  as  it  will,  in  a  stoneware  jar,  then  three  ounces  of 
sulphuric  acid  is  added  to  it  very  slowly  while  the  gelatin  is 
being  stirred  with  a  glass  rod.  The  solution  becomes  very 
hot.  When  it  is  cool,  six  and  one-half  ounces  of  aqua  ammo- 
nia is  slowly  stirred  into  the  acidified  gelatin.  This  amount 
of  ammonia  should  turn  the  solution  neutral.  Add  six 
ounces  of  glacial  acetic  acid,  and  make  up  the  whole  to  eighty 
ounces  of  stock  solution.  Use  one  ounce  of  this,  in  place  of 
acetic  acid,  to  every  twenty  ounces  of  developer,  and  you  will 
remark  the  ease  with  which  large  plates  may  be  developed 
and  the  great  intensity  secured  without  fogging. 

The  reason  for  it  is  this:  The  thicker  a  liquid  is,  the 
slower  a  small  particle  can  get  through  it.  When  a  solution 
of  sulphate  of  iron  (developer)  is  flowed  upon  a  glass  plate, 
holding  iodid  and  nitrate  of  silver  which  has  been  acted  upon 
by  light,  each  particle  of  iron  rushes  to  combine  with  a  par- 


32 


horgan's  half-tone 


tide  of  silver.  Without  the  gelatin  or  other  substance  to 
thicken  the  liquid  and  retard  its  progress  these  particles  of 
iron  attach  themselves  to  the  particles  of  silver  in  an  irregular 
manner,  and  when  such  an  image  is  examined  under  a  micro- 
scope it  will  be  found  that  the  deposit  of  silver  and  iron  in 
the  film  looks  like  coarse  black  sand.  Some  of  the  sand 
particles  are  in  the  portions  of  the  film  that  should  be  abso- 
lutely transparent.  This,  to  the  eye,  is  what  is  termed  "  fog." 
With  the  gelatin  in  the  developer  to  obstruct  the  particles  of 
iron  the  developed  film  when  seen  under  the  microscope  is 
much  finer  in  the  grain,  the  deposit  taking  place  only  where 
the  light  has  acted  upon  the  film,  and  the  edges  of  the  lines 
are  smooth  and  sharp  in  comparison  with  the  ragged-edge 
line  shown  when  the  developer  is  used  without  gelatin. 

GET  IT  IN  THE  NEGATIVE. 

This  is  one  of  the  refinements  in  photographic  work  that 
makes  superior  negatives,  though  known  to  few  operators. 
Where  large  negatives  are  wanted  this  gelatinous  addition  to 
the  developer  permits  an  evenness  of  development  quite 
impossible  without  its  use,  when  handling  large  work  for 
lithographic  or  offset-press  printing.  The  basis  of  all  photo- 
process  work  is  the  negative,  and  that  should  always  be  the 
best  possible,  for  no  amount  of  work  afterward  will  make  up 
for  deficiencies  in  the  negative.  It  was  recognition  of  this 
fact  that  brought  the  writer  so  many  compliments  for  his 
brief  article  in  Penrose's  Pictorial  Annual  for  1909-10,  enti- 
tled "  Get  It  in  the  Negative." 

DEVELOPING  THE  IMAGE. 

A  perfect  negative  being  the  basis  of  all  good  process- 
work,  and  as  the  quality  of  the  negative  is  determined  only 
after  development,  it  can  be  seen  how  important  it  is  that  this 
operation  be  performed  intelligently.  The  first  thing  to  be 
learned  is  to  flow  over  the  exposed  collodion  plate,  in  one 
uninterrupted  sweep,  only  just  enough  developer  to  cover  the 
plate  without  allowing  any  of  the  developer  to  spill  over  the 
edges  of  the  plate.   This  might  seem  easy  to  do,  and  when 


PHOTOLITHOGRAPHY 


33 


the  beginner  tries  it  a  few  times  and  fails  he  thinks  it  is 
impossible  of  performance;  still  the  men  who  are  making 
the  best  negatives  do  not  allow  much  if  any  of  the  developer 
to  leave  the  plate  during  development.  In  fact  the  expe- 
rience and  skill  of  the  wet-plate  photographer  can  be  told  by 
the  success  in  which  he  holds  the  developer  on  the  plate. 

The  reason  for  this  care  in  flowing  the  developer  over  the 
plate  is  that  besides  the  iodid  and  bromid  of  silver,  which 
comprise  the  sensitive  substances  on  which  the  image  is 
impressed  by  light  action,  there  is  an  amount  of  what  is 
termed  "  free  silver  "  on  the  surface  of  the  film  which  is 
necessary  for  the  proper  development  and  intensity  of  the 
image  when  the  iron  solution  is  flowed  on.  If,  with  the  first 
sweep  of  the  developing  solution  over  the  plate,  this  free 
silver  is  washed  off,  then  the  image  developed  will  be  so  much 
the  weaker  in  density. 

FREE  SILVER  NECESSARY  IN  DEVELOPMENT. 

To  prove  the  necessity  of  this  free  silver  in  the  develop- 
ment of  the  image  it  is  only  necessary  to  sensitize  a  collodion 
plate  as  usual,  then  wash  off  the  free  silver  under  the  tap 
before  exposing  the  plate  in  the  camera,  and  afterward  try 
the  development  of  it.  Then  sensitize,  and  wash  off  the  free 
silver  from  a  second  plate.  Expose  it  to  light,  but  before 
development  dip  it  in  the  silver  bath  again,  and  then  see  the 
difference.  The  latter  will  appear  to  have  the  greater  sensi- 
tiveness, as  it  will  develop  into  the  better  negative. 

The  developer  works  best  at  a  temperature  of  6o°  F.,  and 
does  not  work  well  when  it  is  so  old  that  it  appears  brown  in 
color. 

After  proper  development  the  negative  requires  sufficient 
washing  under  the  tap.  It  might  be  advised  here,  in  all 
washing  of  negatives  under  the  tap,  to  get  the  habit  of  per- 
mitting the  full  force  of  the  water  to  strike  a  corner  of  the 
plate  and  flow  over  the  image,  and  not  let  it  flow  directly  on 
the  image.  Many  a  negative  is  injured  by  particles  of  solid 
matter,  in  the  flowing  water,  striking  the  plate  and  punctur- 
ing the  film  where  the  damage  was  irreparable. 

3 


34 


morgan's  half-tone 


Cyanic!  of  potassium,  in  the  proportion  of  one  ounce  to 
twenty-four  ounces  of  water,  is  the  proper  solution  for  fixing 
the  negative.  It  should  be  used  in  a  glass  bathholder  similar 
to  the  one  used  as  a  container  of  the  silver-bath  solution. 
Should  it  be  necessary  to  use  the  cyanid  solution  in  a  tray,  it 
must  be  provided  with  a  cover.  The  common  practice  of 
using  cyanid  of  any  strength,  out  of  a  bottle,  and  pouring  it 
on  the  negative  is  all  wrong.  The  fumes  of  cyanid  are 
injurious  to  health,  and  as  cyanid  above  a  certain  strength 
will  not  only  dissolve  away  the  unacted  upon  salts  of  silver 
in  the  plate  but  attack  the  silver  of  which  the  image  is  com- 
posed, it  will  be  understood  that  when  overstrong  cyanid  is 
poured  on  the  negative  it  destroys  some  of  the  image  where 
the  flow  is  greatest.  By  using  a  bathholder  and  allowing 
some  seconds  for  the  cyanid  solution  to  clear  the  negative, 
all  this  danger  is  avoided.  It  may  be  unnecessary  to  warn 
users  of  cyanid  as  to  its  poisonous  properties,  but  it  is  not 
so  well  known  that  any  acid  reaching  cyanid  of  potassium 
evolves  hydrocyanic  acid,  which  is  the  dangerous  gas  com- 
monly known  as  prussic  acid  gas.  By  way  of  warning,  it 
might  be  added  that  three  grains  of  cyanid  of  potassium 
taken  internally  is  fatal.  * 

INTENSIFICATION. 

A  good  rinsing  of  the  negative  from  all  traces  of  the 
cyanid  of  potassium  should  precede  intensification.  As  we 
are  considering  only  the  methods  of  producing  a  perfect 
negative  for  planographic  printing  we  will  use  an  ideal 
intensifier  made  up  as  follows :  First  make  up  the  following 
three  solutions : 


1.  Bichlorid  of  mercury  120  grains 

Water    12  ounces 

2.  Iodid  of  potassium  180  grains 

Water    4  ounces 

3.  Hyposulphit  of  soda  240  grains 

Water    4  ounces 


Pour  the  second  solution  into  the  first,  making  a  beautiful 
red  emulsion,  iodid  of  mercury.    While  stirring  this  emul- 


PHOTOLITHOGRAPHY  35 

sion  add  the  third  solution,  when  the  red  color  will  disappear. 
Pour  this  transparent  solution  over  the  negative  and  it  will, 
when  it  is  continued  sufficiently  and  penetrates  the  film,  give 
a  beautiful  density  without  harshness  or  danger  of  filling  up 
the  fine  transparent  lines. 

One  point  must  be  advised  strongly  here,  and  that  is  not  to 
do  any  "cutting,"  as  is  customary  in  half-tone  negative- 
making,  on  a  line  negative.  It  may  be  said  to  make  the  final 
printed  result  "  muddy  "  as  a  reproduction.  When  an  opera- 
tor does  any  "  cutting  "  on  a  line  negative  he  shows  that  he 
is  unfamiliar  with  the  principles  that  go  to  perfect  line  repro- 
duction by  any  process. 

INTENSIFICATION  WITH  MERCURY. 

Another  suitable  intensifier  for  the  negative  that  does  its 
work  without  producing  harshness  is  bichlorid  of  mercury. 
The  strength  of  the  solution  used  does  not  much  matter.  It 
can  be  a  saturated  solution,  when  it  works  quickest,  while 
the  more  dilute  it  is  the  slower  it  bleaches  the  film  white. 
It  should  be  acidified  with  a  few  drops  of  hydrochloric  acid 
before  use.   Here  is  a  definite  formula  for  it  commonly  used  : 


Bichlorid  of  mercury   i  ounce 

Chlorid  of  ammonium   I  ounce 

Water   —  20  ounces 

Hydrochloric  acid   1  dram 


This  mercury  intensifier  had  better  be  used  in  a  tray  kept 
for  that  purpose  exclusively.  The  solution  can  be  rocked 
back  and  forth  over  the  negative  until  it  is  found  by  looking 
at  the  back  of  the  negatives  that  the  film  is  bleached  white 
entirely.  Then  wash  the  negative  well  to  remove  all  trace 
of  bichlorid  of  mercury  from  the  film  other  than  that  taken 
up  by  the  image,  otherwise  a  yellow  stain  will  be  produced 
when  the  film  is  treated  with  the  chemicals  that  blacken  the 
image.  The  slightest  yellow  stain  in  the  transparent  parts  of 
the  negative  adds  considerable  time  to  the  exposure  required 
in  the  printing- frame. 

We  have  a  number  of  agents  that  will  blacken  the  image 
after  it  is  bleached  with  bichlorid  of  mercury.    Sulphid  of 


36 


horgan's  half-tone 


sodium  is  most  generally  used  at  the  present  time.  Ammonia 
at  the  strength  of  about  one  ounce  to  ten  of  water  was 
formerly  used,  or  one  ounce  of  sulphit  of  soda  to  ten  ounces 
of  water.  After  the  image  is  blackened  it  should  be  flowed 
over  with  a  solution  of  say  a  quarter  ounce  hydrochloric  or 
nitric  acid  in  ten  ounces  of  water.  This  removes  at  once  any 
tendency  to  stain.  Should  the  intensification  be  insufficient 
the  operations  may  be  repeated,  though  the  washing  between 
operations  must  be  thorough. 

IODIN  INTENSIFICATION. 

One  of  the  most  delicate  intensifies  is  iodin  used  in  this 
way:  In  ten  ounces  of  water  dissolve  three-quarters  of  an 
ounce  of  iodid  of  potassium  and  then  dissolve  in  it  a  quarter 
ounce  of  iodin  crystals.  Flowing  this  over  the  negative, 
after  it  is  fixed  and  well  washed,  changes  the  image  to  a 
beautiful  cream-yellow  color.  When  the  iodin  has  pene- 
trated through  the  film  the  negative  is  well  washed  and 
flowed  with  one  ounce  of  sulphid  of  ammonium  in  four 
ounces  of  water  and  washed  again. 

The  regular  photoengraver  reading  the  list  of  these 
intensifies  will  notice  that  the  copper  and  silver  intensifier 
he  is  best  acquainted  with  from  constant  use  has  been  omit- 
ted. The  omission  is  intentional.  Copper  and  silver  is  useful 
in  its  proper  place  as  an  intensifier,  but  the  intensifies  given 
are  better  for  the  work  now  under  consideration  where  great 
intensity  in  a  negative  is  not  so  essential  as  that  the  smooth- 
ness of  the  edges  of  the  lines  be  preserved  as  well  as  the  rela- 
tive gradations  in  the  widths  of  lines  or  dots  as  found  in  the 
copy,  and  this  copper  and  silver  does  not  preserve,  while 
"  cutting  "  the  negative  destroys  the  relative  gradations. 

"photographing  by  steam/' 

When  J.  Trail  Taylor,  late  editor  of  the  British  Journal 
of  Photography,  visited  this  country,  it  was  the  writer's 
privilege  to  show  him  through  the  various  rooms  in  which 
the  "  Graphic  "  process  was  performed.  The  article  which 
he  wrote  describing  what  he  saw  was  entitled  "  Photograph- 


PHOTOLITHOGRAPHY 


37 


ing  by  Steam."  The  reason  for  this  was  that  he  found  we 
plunged  the  negative  into  tanks  of  almost  boiling  water  after 
developing,  fixing  and  intensification  to  quickly  wash  them 
free  from  chemicals  not  wanted. 

These  tanks  were  wooden  boxes,  lead-lined,  in  which 
there  was  a  steam-pipe  open  at  the  end  so  that  "  live  "  steam 
could  be  turned  on  and  boil  the  water,  if  necessary,  in  the 
tank.  By  holding  a  large-sized  negative  by  one  of  its  corners 
and  plunging  it  quickly  into  the  almost  boiling  water,  the 
heat  striking  the  glass  equally  on  both  sides  prevented 
unequal  expansion  and  any  danger  of  cracking  the  glass. 
The  hot  water  removed  the  superfluous  chemicals  almost 
immediately,  so  that  the  speed  with  which  we  turned  out 
large  negatives  in  those  days  by  this  application  of  steam 
to  photography  would  make  some  of  the  modern  "  records  " 
appear  ridiculous. 

PROTECTING  THE  NEGATIVE  FILM. 

The  most  valuable  application  of  steam  was  in  the  final 
rinsing.  In  the  steam-heated  drier  was  a  glazed  teapot  of 
hot  gum-arabic  solution,  and  the  hot-water  tank  for  the  final 
rinse  was  close  to  the  drier,  so  that  the  instant  the  negative 
was  drawn  out  of  the  hot  water  it  was  flowed  with  the  solu- 
tion of  hot  gum  and  the  door  of  the  drier  closed  on  it  quickly 
so  that  it  was  dry  in  a  few  seconds.  This  method  of  drying 
negatives  and  protecting  the  film  from  scratching  can  not 
well  be  improved  upon. 

RETOUCHING  THE  NEGATIVE. 

Every  negative  should  be  inspected  in  a  retouching- 
frame  before  being  printed  from.  All  holes  in  the  film  or 
transparent  spots  not  wanted  should  be  stopped  out  with  an 
opaque  pigment  like  India  ink  thickened  with  gum  arabic. 
This  dispenses  with  the  troublesome  scraping,  to  remove 
these  blemishes,  when  they  reach  the  planographic  trans- 
ferrer. 

More  important  than  stopping  out  these  spots  is  the  exam- 
ination of  the  transparent  lines  to  see  that  they  are  not  acci- 


38 


horgan's  half-tone 


dentally  broken  anywhere.  These  broken  or  filled-in  lines 
occur  most  frequently  from  weak  lines  in  the  drawing-  not 
seen  by  the  artist.  When  these  lines  are  mechanical  and 
perfectly  straight  they  can  be  etched  in  on  the  negative  with 
a  needle  point  moved  along  the  side  of  a  metal  straight-edge. 
Or  when  they  are  curved  various  shapes  of  artists'  drawing, 
curves  in  celluloid  may  be  used  to  guide  the  needle.  Cellu- 
loid triangles  also  will  be  found  indispensable  for  this  work. 
Should  the  weak  lines  be  made  by  free-hand  drawing,  such 
as  are  found  in  maps,  cartoons  or  pen-and-ink  sketches,  these 
delicate  lines  can  also  be  cleaned  up  in  the  negative,  though 
the  work  should  be  done  by  one  with  artistic  training.  When 
the  filled-in  lines  in  the  negative  come  from  gray  lines  in  a 
piece  of  wood-engraved  or  intaglio-engraved  copy,  it  is  diffi- 
cult to  imitate  them  with  a  needle-point  in  the  negative.  No 
negative  should  be  printed  from  which  has  any  blemishes  that 
can  be  removed. 

PHOTOLITHOGRAPHY. 

From  the  negative  we  will  first  consider  the  production  of 
a  photolithographic  transfer,  as  this  is  the  most  convenient 
method  of  getting  designs  on  the  offset  press  or  on  stone  or 
metal  when  printed  from  in  the  planographic  manner.  When 
large  maps  are  to  be  joined  together,  or  when  illustrations 
are  to  be  inserted  in  a  border,  or  lines  of  type  to  be  added  to 
maps  or  illustrative  matter,  there  is  no  easier  method  of 
doing  all  of  this  than  by  using  transfers.  All  of  which  is 
known  to  the  lithographer,  but  not  to  those  handling  the 
offset  press,  who  are  not  trained  lithographers. 

The  method  of  making  the  ideal  photolithographic  trans- 
fer paper  has  been  fully  described,  and  this  is  the  way  to 
make  use  of  it:  It  is  printed  upon  from  the  negative  in  an 
ordinary  photographic  printing-frame  just  as  a  piece  of  regu- 
lar printing-out  paper.  That  is,  in  a  room  lit  by  yellow  light, 
a  piece  of  the  sensitized  photolithographic  paper,  large 
enough  to  cover  the  negative,  is  placed  in  the  printing- frame 
behind  the  negative,  and  the  whole  exposed  to  sunlight  for 
about  thirty  or  forty  seconds,  or  until  the  image  shows  a 


PHOTOLITHOGRAPHY 


39 


bright  brown  against  the  yellow  ground  of  the  paper.  The 
fact  that  the  print  can  be  examined  and  the  correct  exposure 
determined  by  the  color  of  the  exposed  image  prevents  any 
uncertainty  in  timing  the  length  of  the  exposure  to  light. 

INKING  THE  PHOTOLITHOGRAPHIC  PAPER. 

The  best  way  to  cover  the  photolithographic  prints  with 
an  even  film  of  transfer  ink  is  to  lay  them  face  down  on  a 
lithographic  stone  or  polished  zinc  plate  that  has  been  rolled 
up  with  an  even  film  of  such  ink.  The  prints  should  be 
dampened  before  coating  with  ink,  and  instead  of  laying 
them  between  damp  blotters  in  a  dampening  book  it  is  recom- 
mended that  they  be  placed  in  a  dampening  closet  arranged 
like  this : 

A  cabinet  containing  shallow  drawers  about  an  inch  deep 
has  galvanized  wire  open-mesh  screen  substituted  for  the 
bottoms  of  the  drawers.  Into  the  top  and  bottom  drawers, 
as  well  as  every  alternate  drawer,  are  laid  wet  blotters,  the 
photolithographic  prints  to  be  dampened  being  laid  on  the 
wire  screens  in  the  bottom  of  the  alternate  drawers  that  are 
without  blotters.  In  this  way  the  photolithographic  prints 
absorb  moisture  from  the  wet  blotters  without  coming  into 
contact  with  them.  When  the  prints  in  the  drawers  are  limp 
they  are  sufficiently  damp  to  be  laid  face  down  on  the  inked 
stone  or  metal  plate  and  run  through  the  press. 

THE  TRANSFER  INK. 

The  transfer  ink  can  be  the  one  that  the  transferrer 
approves  of,  for  there  is  a  wide  range  in  the  choice.  The 
writer  has  been  successful  with  an  ink  composed  of  five  parts 
of  German  transfer  ink,  softened  with  No.  o  varnish  and 
mixed  with  four  parts  of  crayon  ink,  softened  with  oil  of 
lavender.  Other  transferrers  prefer  equal  parts  of  transfer 
ink  and  lithographic  printing-ink  ground  in  No.  o  varnish, 
while  what  is  known  as  stone-to-stone  transfer  ink  answers 
very  well.  One  thing  that  can  be  stated  with  certainty  is 
that  there  is  no  excuse  for  any  one  making  his  own  ink,  as 
recommended  in  the  books,  for  much  better  ink  than  they 


40 


horgan's  half-tone 


can  possibly  make  is  to  be  had  at  any  lithographic  supply 
house. 

It  should  be  said  that  the  film  of  ink  on  the  paper  can 
preferably  be  so  thin  that  the  yellow  tone  of  the  paper  shows 
through  the  ink.  When  the  prints  are  laid  on  the  inked  stone 
or  metal  and  pulled  through  the  press  they  are  pulled  from 
the  stone  and  laid  down  in  their  places  reversed,  so  as  to 
insure  a  more  even  coating  and  also  that  every  spot  of  the 
print  may  be  covered  with  ink. 

DEVELOPING   PHOTOLITHOGRAPHIC  TRANSFERS. 

The  inked  prints  are  now  floated  for  a  few  minutes  on 
the  surface  of  water  that  is  nearly  boiling,  when  the  ink  takes 
on  a  beautiful  gloss.  Some  practice  is  required  in  floating 
the  prints,  as  they  curl  up  if  not  prevented  from  doing  so, 
and  the  hot  water  getting  over  the  face  is  liable  to  spoil  the 
transfer.  Floating  on  water  almost  to  the  boiling  point 
softens  the  ink  and  draws  it  into  absolute  contact  with  the 
light-hardened  image  on  the  paper  at  the  same  time  the 
water  penetrates  through  the  unhardened  gelatin  coating  and 
repels  the  ink  from  its  surface.  This  can  be  determined  when 
the  inked  print  begins  to  lose  its  original  gloss.  The  print 
is  then  removed  to  the  wet  surface  of  a  sheet  of  plate  glass, 
laid  on  it,  and  with  a  wet  soft  Turkish  sponge  the  ink  is 
washed  away  from  the  gelatin  surface  where  the  light  has 
not  acted  upon  it,  leaving  an  image  in  sharp  lines  of  transfer 
ink.  The  print  is  plunged  into  clean  water  and  left  until  all 
of  the  soluble  bichromate  of  potash  is  dissolved  out  of  it, 
when  it  is  hung  up  to  dry.  While  drying,  all  water  spots 
that  rest  on  the  image  must  be  removed  with  the  edge  of 
pieces  of  blotter  because  they  contain  a  slight  trace  of  gelatin 
which,  drying  on  the  lines,  would  prevent  them  transferring. 
When  the  transfers  are  dry  they  are  ready  to  be  transferred 
to  lithographic  stone,  aluminum,  or  zinc  plates,  either  for 
direct  printing  from  zinc  or  from  zinc  on  the  offset  press 
after  reversal. 


A  COLLOTYPE 


COLLOTYPE. 

METHOD  OF 

PRINTING  FROM  GELATIN  IN  THE  LITHOGRAPHIC 
MANNER. 


Collotype  is  one  of  the  earliest  of  the  photomechanical 
printing  processes.  In  Germany,  where  it  is  worked  most 
successfully,  it  is  called  lichtdruck,  in  France,  phototypie, 
and  in  the  United  States  it  is  known  as  albertype,  artotype, 
heliotype,  autogravure  and  plain  gelatin  printing.  Its 
proper  title  is  collotype,  and  it  has  come  down  to  us  from 
Louis  Alphonse  Poitevin,  a  French  chemist  and  engineer, 
who  received  a  prize  for  the  process  in  1855.  It  was 
improved  upon  since  that  time  by  Tessier  du  Mothay,  Lemer- 
cier,  Albert,  Obernetter,  Husnik,  Sprague,  Sawyer,  Colonel 
Waterhouse,  Ernest  Edwards,  T.  C.  Roche,  and  others. 
So  the  method  has  proved  worthy  of  the  attention  of  the 
brightest  experimenters  in  photomechanical  printing. 

The  results  possible  of  attainment  by  collotype  are 
deserving  of  study  by  processworkers  and  particularly  those 
with  a  knowledge  of  lithography. 

THE  PRINCIPLE  OF  COLLOTYPE. 

Collotype  is  a  process  by  which  a  film  of  gelatin  is  made 
selective  of  either  greasy  ink  or  water  so  that  it  may  be 
printed  from  in  a  lithographic  manner.  The  gelatin  is  sen- 
sitized with  a  bichromate  and  given  a  grain  on  drying. 
This  sensitized  gelatin  is  exposed  under  an  ordinary  pho- 
tographic negative,  washed  and  dried,  and  then  treated  some- 
what similar  to  a  lithographic  stone,  to  which  it  shows 
corresponding  properties.  It  is  a  simple  process,  which  has 
been  successfully  carried  out  by  amateurs  at  photography, 
though  it  is  so  sensitive  to  fluctuations  of  temperature  and 
humidity  that  it  has  been  worked  more  easily  in  countries 
having  a  more  equable  climate  than  that  of  some  portions 
of  the  United  States,  and  still  with  our  present  methods  of 

41 


42 


horgan's  half-tone 


producing  artificial  climates  in  a  factory  there  is  nothing 
now  to  prevent  this  process  being  worked  anywhere. 

THE  SUBSTRATUM. 

The  first  difficulty  the  early  workers  had  with  the  process 
was  that  the  gelatin  film  would  strip  from  its  support,  which 
was  usually  glass.  This  was  overcome  by  giving  the  glass 
a  fine  grain  and  coating  this  glass  with  a  mixture  of 
bichromate  and  gelatin  which  was  exposed  to  light  through 
the  glass  support.  By  this  means  an  insoluble  film  was  had 
on  the  glass,  which  held  the  subsequent  coating  secure. 
Later  it  was  found  that  silicate  of  soda  (water  glass)  and 
an  organic  substance  made  a  suitable  substratum,  while  the 
graining  of  the  glass  was  essential.  T.  C.  Roche,  of  New 
York,  used  copper  instead  of  glass  as  a  support,  and  Ernest 
Edwards,  of  Boston,  stripped  the  collotype  film  so  that  it 
could  be  attached  to  zinc  or  any  support.  The  highest 
grade  collotypes  are  printed  from  plate  glass  about  one- 
half  inch  thick  which  has  been  ground  with  fine  emery 
powder,  care  being  taken  that  no  scratches  occur  or  they 
will  appear  in  the  print.  After  washing  and  drying,  the 
ground  plate  glass  is  put  on  leveling  screws  in  a  drying 
closet  free  from  dust  and  flowed  with  the  following  sub- 
stratum : 

Distilled  water  10  ounces 

Whites  of  fresh  eggs   5  ounces 

Silicate  of  soda   2  ounces 

The  eggs  must  be  beaten  to  a  froth  and  allowed  to  settle, 
and  the  whole  mixture  shaken  thoroughly  before  being  fil- 
tered ;  remembering  always  that  the  enemies  of  perfect  collo- 
type plates  are  bubbles  and  dust,  so  that  every  precaution 
must  be  taken  against  them.  In  filtering,  which  must  be 
carefully  done,  the  mixture  is  carried  from  the  bottom  of 
the  funnel  to  the  sides  of  the  vessel  to  prevent  bubbles. 

COATING  WITH  SUBSTRATUM  AND  GELATIN. 

A  small  quantity  of  the  substratum  is  poured  on  the 
leveled  glass  plate  and  pushed  over  the  whole  surface  with 


COLLOTYPE  43 

a  glass  rod,  taking  care  not  to  form  air  bubbles.  The  plate 
can  then  be  stood  up  in  an  ordinary  plate  rack  to  dry. 

The  actual  sensitive  coating  may  be  prepared  as  follows, 
though  each  collotyper  has  his  own  pet  formula. 

There  are  so  many  kinds  of  gelatin  to  choose  from  — 
Nelson's,  Heinrich's,  Creuz's,  Russian,  Swiss,  French  — 
that  it  is  impossible  to  advise.  What  is  wanted  is  a  mid- 
dling hard  gelatin,  though  this  can  be  regulated  somewhat 
by  the  amount  of  chrome  alum  added  to  the  gelatin.  A 
simple  formula  is  as  follows : 


"  Middle  hard  "  gelatin   2  ounces 

Water   20  ounces 

Bichromate  of  potash  TA  ounce 

Ammonia,  26  0  U.  S.  P  %  ounce 


Use  water  that  has  been  boiled  to  minimize  the  risk  of 
bubbles,  melt  the  gelatin  in  the  water  by  heat,  stir  in  the 
bichromate  and  the  ammonia  and  pour  in  one-fourth  ounce 
of  a  ten  per  cent  solution  of  chrome  alum.  The  quantity 
of  chrome  alum  will  vary  with  the  character  of  the  gelatin. 
The  gelatin  must  be  stirred  briskly  while  the  hardening  solu- 
tion of  chrome  alum  is  being  added.  The  gelatin  solution 
must  be  kept  at  a  temperature  not  above  ioo°  F.  When 
filtering,  either  a  double  funnel  must  be  used,  the  outer  one 
containing  hot  water,  or  a  tin  pail  can  be  taken  and  a  hole 
made  in  the,  center  of  the  bottom  through  which  the  spout 
of  a  tin  funnel  projects  and  is  soldered  there.  By  keeping 
hot  water  in  the  pail  the  gelatin  mixture  can  be  filtered 
through  clean  muslin  to  a  pitcher  below  which  is  standing 
in  a  vessel  of  warm  water. 

DRYING  THE  GELATIN -COATED  PLATES. 

A  suitable  drying  closet  or  room  is  prepared  for  the 
drying  of  the  plates.  Its  construction  will  depend  on  the 
number  and  size  of  the  plates  to  be  used  and  the  arrange- 
ment of  the  workrooms.  What  is  required  is  a  place  illu- 
minated by  a  yellow  light,  free  from  dust,  and  where  a 
temperature  of  from  no°  to  1200  F.  can  be  maintained. 
It  also  must  have  rests  for  the  pieces  of  plate  glass  that 


44 


horgan's  half-tone 


will  bring  the  latter  absolutely  level  when  tested  in  all  direc- 
tions with  a  spirit  level. 

The  pieces  of  plate  glass  are  placed  on  the  leveled  stands, 
and  after  careful  dusting  are  flowed  with  some  of  the  warm 
gelatin  mixture  in  the  proportion  of  one  ounce  to  120  square 
inches  of  plate-glass  surface.  The  solution  is  spread  with 
a  glass  rod,  avoiding  air  bubbles,  and  is  then  allowed  to 
dry.  The  temperature  at  which  the  film  dries  affects  the 
grain.  Dried  at  no°  F.  the  grain  is  too  fine;  dried  at  1400 
F.  the  grain  is  too  coarse,  so  that  about  1200  F.  will  produce 
the  most  satisfactory  grain. 

Besides  being  preserved  from  dust  and  white  light  while 
drying,  vibration  will  cause  wavy  markings  and  drafts  will 
give  it  an  uneven  grain. 

THE  NEGATIVE  AND  PRINTING. 

A  reversed  negative  on  crystal  plate  glass  must  be  used, 
and  this  can  be  had  by  the  use  of  a  prism  or  by  stripping 
and  turning  as  explained  elsewhere  in  this  book.  The  nega- 
tive should  be  one  with  perfect  gradations.  The  dimen- 
sions of  the  print  must  be  indicated  by  strips  of  tin-foil 
secured  to  the  negative.  The  crystal  plate  glass  negative 
with  its  mask  of  tin- foil  is  laid  in  the  special  deep  printing- 
frame  used  for  collotype,  and  the  sensitized  plate  glass  laid 
upon  it  and  good  pressure  applied ;  black  velvet  and  pure 
gum  rubber,  or  felt  blanket,  being  used  as  a  backing  in  the 
printing-frame. 

The  exposure  can  best  be  timed  through  the  use  of  an 
actinometer,  of  which  there  are  numerous  patterns  in  the 
market.  After  printing  the  gelatin-coated  plate  glass  it 
is  allowed  to  soak  in  cold  water  for  an  hour  or  more,  or 
until  the  bichromate  is  dissolved  out.  The  yellow  color  is 
fixed  by  the  action  of  light  in  the  shadows,  but  will  wash 
out  of  the  high  lights  readily.  Now  dry  the  plate  and  it  is 
ready  for  printing  in  ink. 

ETCHING  AND  PRINTING. 

For  practical  commercial  work  a  trained  lithographer 
should  undertake  the  printing.    He  is  provided  with  litho- 


COLLOTYPE 


45 


graphic  presses,  the  lithographic  and  composition  rollers, 
and  the  stiff  and  thin  inks  necessary.  Space  does  not  per- 
mit any  directions  for  printing,  only  to  give  what  is  called 
an  "  etching "  solution  which  lithographers  are  not  usually 
acquainted  with. 

Equal  parts  of  water  and  glycerin  to  which  from  one 
and  one-half  to  two  per  cent  of  table  salt  is  added  makes 
a  good  "etching"  solution.  The  object  of  this  "etching" 
solution  is  to  make  the  gelatin  film  hygroscopic  so  that  it 
will  retain  moisture  where  the  light  has  not  hardened  the 
gelatin,  and  a  number  of  impressions  may  be  pulled  with- 
out redamping.  The  plate  is  allowed  to  soak  in  this  "  etch- 
ing "  solution  for  a  few  minutes  or  an  hour  or  two,  depend- 
ing on  the  weather,  the  character  of  the  image,  and  whether 
it  is  to  be  used  on  the  hand  press  or  the  steam  press.  The 
plate  can  be  leveled,  as  before,  and  the  "  etching  "  solution 
poured  on  it,  and  this  is  the  usual  practice. 

Presses  for  collotype  printing  have  clamps  for  holding 
the  glass  plate  secure  to  the  bed.  Formerly  they  were 
imbedded  in  plaster  of  paris  on  the  bed  of  the  press. 

When  the  "  etching  "  solution  has  remained  long  enough 
on  the  plate  it  is  soaked  off  with  a  soft,  damp  sponge  and 
the  surface  moisture  removed  with  a  soft,  lintless,  dry 
cloth.  The  plate  is  first  inked  with  a  litho  roller  and  a 
stiff  ink  for  the  shadows,  and  then  inked  with  a  composition 
roller  and  a  much  thinner  ink  for  the  middle  tones  and  the 
delicate  shading  in  the  high  lights.  The  paper  used  to 
print  upon  is  specially  made  for  collotype  printing.  The 
two  inks  used  are  usually  two  shades  of  the  same  color, 
though  different  colors  can  be  used. 

The  results  produced  by  collotype  printing  can  have  all 
the  gradations  of  the  photograph,  from  which  it  is  difficult 
sometimes  to  distinguish  it,  though  it  has  the  advantage 
that  it  is  made  in  permanent  printing-ink,  so  that  for  fine 
book  illustration  and  permanent  records  such  as  govern- 
ment publications,  and  for  small  and  choice  editions  of  illus- 
trated work,  it  can  not  be  approached  by  typographic 
methods. 


46 


horgan's  half-tone 


COLLOIDS  USED  IN  COLLOTYPE. 

GELATIN. 

Gelatin  is  produced  by  boiling  bones,  hoofs,  horns  and 
the  clippings  from  hides,  calves'  feet  and  other  animal  sub- 
stances. It  contains  about  fifteen  to  twenty  per  cent  of 
water  at  normal  temperatures,  and  in  cold  water  will  swell 
up  and  absorb  from  five  to  ten  times  its  own  weight  of 
water.  It  becomes  a  solution  when  raised  above  900  F. 
and  jellies  on  cooling.  Gelatin  keeps  indefinitely  in  the  dry 
state,  but  dissolved  in  water  it  soon  putrefies,  turns  first 
acid  and  then  alkalin,  giving  off  ammoniacal  gas.  Alum, 
alcohol,  carbolic,  boracic  and  salicylic  acids,  thymol,  for- 
malin and  the  salts  of  zinc  act  as  preservatives  of  gelatin. 
Acetic,  hydrochloric,  sulphuric  and  oxalic  acids  dissolve 
gelatin  even  when  cold.  Gelatin  dissolved  in  acetic  acid 
makes  a  very  useful  liquid  glue.  Carbolic  acid  and  alcohol 
will,  when  in  excess,  precipitate  gelatin  from  water  solu- 
tions. The  alkalin  bichromates  in  combination  with  gela- 
tin render  the  latter,  after  exposure  to  light,  insoluble  and 
incapable  of  absorbing  water  —  this  action  being  the  basis 
of  nearly  all  the  photomechanical  printing  processes. 
Chrome  alum  and  tannin  render  gelatin  insoluble,  though 
capable  of  absorbing  water.  Gelatin  heated  for  a  long  time 
loses  its  swelling  property  and  is  called  metagelatin. 

ISINGLASS. 

The  purest  form  of  gelatin  comes  from  the  fish  and  is 
called  isinglass.  The  best  quality  is  produced  in  Russia 
from  the  sturgeon.  In  the  United  States  it  is  made  from 
several  kinds  of  fish,  including  the  sturgeon.  In  the  East 
Indies  they  produce  an  isinglass  from  seaweed  which  is 
called  agar-agar.  Many  collotype  printers  prefer  isinglass 
to  gelatin  and  it  is  sometimes  used  in  the  enamel  process. 


FOUR-COLOR  ROTARY  PHOTOGRAVURE. 
Van  Dyck  Gravure  Co.,  New  York. 
Courtesy  of  the  National  Art  Co. 


PHOTOGRAVURE. 


BY  ART  LOVERS 

RECOGNIZED  AS  THE  MOST  BEAUTIFUL  OF  ALL 
PHOTOMECHANICAL  PROCESSES. 


Intaglio  engraving  was  the  aim  of  the  first  experimenters 
seeking  methods  of  applying  photography  to  the  printing- 
press.  And  a  remarkable  thing  about  it  is  that  the  methods 
they  worked  out  as  pioneers  have  not  been  greatly  improved 
upon  since,  at  least  in  the  fundamental  principles.  When 
Nicephore  Niepce,  in  1824,  coated  a  metal  plate  with  a  solu- 
tion of  asphalt  and  exposed  it  to  light  under  a  positive  engra- 
ving and  then  developed  and  etched  that  portrait  of  Cardinal 
d'Amboise,  he  had  discovered  the  whole  application  of  pho- 
tography to  intaglio  engraving. 

So  it  was  with  photogravure.  When  William  Henry 
Fox-Talbot,  October  29,  1852,  received  his  patent  "  For 
engraving  pictures,  obtained  by  photographic  processes  on 
steel  plates;  the  engraved  plates  can  be  printed  from,"  he 
had  laid  down  the  principles  of  photogravure  as  it  is  prac- 
ticed to-day.  And  when  in  the  same  patent :  "  To  produce 
the  effect  of  engraved  lines,"  he  impressed  the  image  of  a 
piece  of  gauze  "  upon  the  gelatin  prior  to  the  image  of  the 
object  required  being  formed,"  he  had  discovered  the  prin- 
ciple which  makes  rotary  photogravure  possible  in  our  time. 

Talbot  covered  a  metal  plate  with  a  thin  film  of  bichro- 
matized  gelatin,  exposed  this  to  the  action  of  light  under  a 
positive,  washed  away  the  unhardened  gelatin  and  etched  the 
plate.  In  his  patent  of  April  21,  1858,  he  improved  on  this 
idea  by  dusting  the  gelatin  with  a  powdered  resin  and 
etched  with  perchlorid  of  iron,  just  as  we  do  to-day.  He 
also  took  a  mold  from  his  developed  gelatin  plate  in  gutta- 
percha and  produced  an  intaglio  printing-plate  by  electro- 
deposition,  the  principle  on  which  some  of  the  finest  photo- 
gravures are  now  made. 

47 


48 


horgan's  half-tone 


There  are  at  present  two  methods  of  photogravure  in  use, 
as  Talbot  devised  them.  One  process  produces  what  are 
known  as  "  bitten  "  plates,  the  other  as  "  grown  "  plates.  A 
bitten  plate  is  one  in  which  the  photographic  image  is  pro- 
duced on  the  metal  plate,  and  the  latter  etched  or  bitten  with 
an  acid  or  mordant.  Grown  plates  are  electrotypes  from 
either  silvered  glass  plates  or  silvered  copper  plates,  on  which 
a  bichromatized-gelatin  image  has  been  produced  in  relief  by 
photography.  Bitten  plates  are  more  common,  while  grown 
plates  are  used  by  Goupil  and  many  of  the  large  art-publish- 
ing houses  of  Europe.  The  regular  rolled  or  hammered  cop- 
per is  used  for  the  bitten  plate,  while  the  grown  copper  plate, 
being  the  product  of  electro-deposition,  formerly  there  was 
a  danger  that  the  first  copper  deposited  would  be  harder  than 
the  rest,  so  that  the  roller  pressure  of  printing  would  curl 
the  plate  and  in  attempting  to  flatten  it  again  it  would  break. 
Electro-deposition  is  now  so  far  under  control  that  this  diffi- 
culty is  no  longer  an  objection  to  the  grown  plate. 

Talbot  began  with  steel  plates,  which  he  etched  with 
bichlorid  of  platinum.  Later  he  turned  to  copper  and  per- 
chlorid  of  iron,  just  as  we  use  at  present.  The  writer  has 
before  him  a  proof  from  one  of  Talbot's  early  plates.  It  is 
a  remarkably  fine  result,  except  that  the  blacks  in  the  proof 
were  not  entirely  solid.  A  mezzotint  engraver  could  have 
corrected  this  fault  readily,  but  Talbot  relied  entirely  on  his 
process  for  results. 

IMPROVEMENTS  BY  CARL  KLIC. 

Photogravure  being  the  most  artistic  of  the  photo- 
mechanical processes  it  was  natural,  therefore,  that  it  should 
attract  the  attention  of  artists,  who  have  done  so  much  to 
perfect  it.  In  fact  one  who  has  not  natural  artistic  feeling 
or  careful  training  will  never  distinguish  himself  at  photo- 
gravure. It  also  naturally  follows  that  photogravure  is  most 
successfully  practiced  in  the  cities  possessing  art  schools. 

To  Carl  Klic,  a  painter  from  Bohemia,  born  in  1841,  we 
owe  most  of  the  improvements  found  in  photogravure  as 
practiced  to-day.    Klic  came  to  the  work  with  a  splendid 


PHOTOGRAVURE 


49 


training.  The  son  of  a  chemist,  he  was  himself  a  practical 
chemist.  His  artistic  bent  brought  him  to  study  at  the 
Academy  of  Painting  at  Prague.  He  subsequently  tried  his 
hand  successfully  as  a  photographer,  lithographic  designer, 
and  as  a  caricaturist  on  Der  Floh  and  other  papers.  Hav- 
ing owned  a  photographic  studio  at  Brunn  he  dreamed 
then  of  the  possibility  of  printing  from  the  photographic 
negative  in  permanent  printing-ink.  He  first  mastered  collo- 
type, and  then  began  —  about  1873  —  experimenting  with 
intaglio  work  on  zinc.  It  was  about  1875  that  he  hit  on  the 
idea  of  combining  a  carbon  print  with  an  aquatint  grain. 

A  peculiarity  of  Klic  was  that  he  never  patented  any  of 
his  inventions,  preferring  to  keep  them  secret,  so  that  it  is 
difficult  to  give  dates  for  any  of  his  doings.  In  1879  he  did 
make  public  something  of  his  methods  of  photogravure.  Pie 
sold  the  process  in  Vienna  to  Victor  Angerer,  and  it  became 
the  foundation  of  great  art  printeries  that  have  made  Aus- 
trian photogravures  the  envy  of  processworkers  everywhere. 

Many  experimenters  were  then  at  work  on  photogravure, 
using  copper  instead  of  steel  and  zinc,  and  using  perchlorid 
of  iron  as  the  mordant.  It  is  said  that  in  1881  Klic  had 
become  completely  successful  in  using  a  carbon  transfer  for 
getting  his  negative  resists  on  copper.  By  this  means  all 
soluble  gelatin,  which  had  made  his  previous  work  uncer- 
tain, was  eliminated. 

GRAIN  DIRECT  ON  THE  COPPER  PLATE. 

Talbot  coated  the  plate  with  bichromatized  gelatin  and 
afterward  laid  an  aquatint  grain  upon  the  gelatin  before 
biting.  Klic  now  laid  on  the  copper  a  grain  of  finely  pow- 
dered bitumen  which  he  fixed  to  the  plate  by  heat.  Upon 
this  grain  he  transferred  a  developed  carbon  print.  This 
grain  secured  the  carbon  film  to  the  plate,  a  feat  which  other 
experimenters  had  found  impossible,  as  the  carbon  transfer 
would,  on  drying,  lift  clear  from  a  polished  copper  plate.  It 
was  to  prevent  this  that  Talbot  gave  his  steel  plates  a  tooth 
by  a  preliminary  etching  before  coating  with  gelatin. 

Klic  also  carried  out  the  etching  with  successive  solutions 
4 


50 


horgan's  half-tone 


of  perchlorid  of  iron  of  different  strengths,  beginning-  with 
the  strongest,  which  bit  through  the  thinnest  parts  of  the 
film,  the  shadows  in  the  plate,  while  the  weakest  solution  of 
iron  was  necessary  to  penetrate  the  thickest  parts  of  the  gela- 
tin covering.  This  is  our  photogravure  method  of  to-day. 
How  simple  it  all  seems,  and  yet  how  many  years  of  patient 
experimenting  it  required.  Many  names  of  experimenters 
and  processes  could  be  given,  but  only  Carl  Klic's  improve- 
ments on  Talbot's  inventions  have  survived. 

ELECTROTYPING  A  DAGUERREOTYPE. 

Daguerre  had  no  sooner  unfolded  his  marvelous  method 
of  recording  camera  images  on  a  silvered  copper  plate  than 
the  brightest  brains  in  every  country  began  to  study  how 
this  copper  plate  could  be  printed  from.  It  was  natural  that 
they  should  try  etching  the  daguerreotype  plate. 

Electro-deposition  of  metals  was  discovered  just  about 
1839,  the  time  that  the  daguerreotype  was  given  to  the 
world.  Attempts  were  made  immediately  to  see  if  by  electro- 
deposition,  011  some  parts  of  the  plate,  a  daguerreotype  could 
not  be  printed  from.  These  experiments  continued  until 
about  1853-4  —  when  Paul  Pretsch  in  Vienna  and  A.  L. 
Poitevin  in  Paris  showed  proofs  from  plates  that  had  been 
made  by  electro-deposition  on  a  film  of  bichromatized  gela- 
tin, which  had  been  exposed  to  light,  swelled  in  water  and 
reticulated  by  chemical  treatment. 

ROTARY  PHOTOGRAVURE  IN  1 854. 

As  an  illustration  of  how  little  there  is  new  under  the 
sun,  at  least  the  photographic  sun,  it  might  be  mentioned 
here  that  Paul  Pretsch  patented  his  method  of  making  pho- 
togravure plates  on  November  9,  1854.  On  August  II,  1855, 
he  received  another  patent  for  applying  his  process  to  the 
engraving  of  copper  cylinders,  copper  or  other  suitable  plates 
engraved  by  the  processes  set  forth,  and  are  used,  he  said, 
"  for  the  formation  of  cylinders  to  be  employed  in  calico  and 
similar  printing."  To-day  men  are  seeking  patents  on  meth- 
ods of  applying  photography  to  the  engraving  of  copper 


PHOTOGRAVURE 


51 


rolls  for  printing,  thinking  that  they  have  discovered  some- 
thing new.  They  are  making  in  New  York  daguerreotype 
images  on  silvered  copper  rolls,  developing  them  with  mer- 
cury and  etching  them  successfully  —  the  idea  which  was 
tried  out  for  years  after  1840  and  pronounced  impossible. 

PHOTOGRAVURE  MAPS. 

Poitevin  was  more  successful  with  his  process  which  he 
patented  December  13,  1855.  So  also  was  Ma*riot  of  Vienna, 
for  in  1869  portions  of  a  map  of  Austria-Hungary  were  pro- 
duced by  grown  photogravure  plates.  In  1872  was  begun 
a  map  of  central  Europe  consisting  of  380  plates,  and  later 
another  map  of  720  plates.  The  publication  of  these  maps 
in  Vienna  attracted  the  attention  of  all  governments,  so  that 
Mariot's  process  of  photogravure  has  since  been  used  in 
many  European  countries  for  mapmaking,  while  Major  J. 
Waterhouse  perfected  the  process  for  government  use  in 
India. 

The  writer  invented  in  1881  an  original  method  of  photo- 
gravure which  since  that  time  would  have  saved  the  Federal 
Government  at  Washington  hundreds  of  thousands  of  dol- 
lars yearly  in  map  engraving.  When  Captain  Sigsbee  was  in 
charge  of  the  Hydrographic  office  he  wanted  this  method 
adopted,  but  the  "  board  "  which  passes  on  improvements 
decided  that  a  photographic  method  would  "  distort."  The 
facts  are,  in  copying  foreign  engraved  maps,  photogravure 
would  give  the  Government  an  absolute  facsimile,  while  the 
present  method  of  tracing  and  retracing  by  hand  leads  to 
innumerable  errors.  And  so  the  United  States  Government 
still  remains  behind  other  countries  in  mapmaking. 

KNOWLEDGE  OF  THE  CARBON  PROCESS  NECESSARY. 

As  before  stated,  the  Talbot-Klic  method  is  the  one  most 
practiced  and  will  be  here  described.  The  carbon  process  is 
a  most  important  feature  of  this  method,  but  as  it  is  a  purely 
photographic  process  outside  the  scope  of  this  book,  which 
treats  only  of  photography  applied  directly  to  the  printing- 
press,  we  can  only  refer  briefly  to  the  carbon  process  here. 


52 


horgan's  half-tone 


The  student  is  referred  to  the  excellent  manuals  published  on 
the  subject. 

Carbon  tissue  for  photogravure  is  purchased  from  a 
dealer  in  photographic  supplies.  It  comes  in  rolls  2><  by 
12  feet  and  consists  of  a  strong  paper  evenly  coated  with 
gelatin  containing  a  pigment  either  brown,  red,  or  sepia. 
The  first  color  is  the  one  most  used,  as  it  shows  stronger  on 
the  copper.  This  tissue  is  sensitized  in  bichromate  of  potash, 
dried,  exposed  to  light  under  a  positive,  transferred  while 
wet  to  the  copper  plate,  and  treated  on  the  back  with  warm 
water,  which  dissolves  the  gelatin  unhardened  by  light.  The 
paper  support  is  stripped  off  and  the  soluble  gelatin  washed 
away,  when  the  image  will  be  found  on  the  copper  in  gelatin 
photogravure  relief  corresponding  to  the  lights  and  shades  of 
the  positive  through  which  the  light  acted.  Where  the  posi- 
tive is  densest,  the  light  penetrated  least  and  the  film  of  gela- 
tin is  consequently  thinnest.  Where  the  positive  was  most 
transparent,  the  light  acted  to  the  greatest  extent,  and  the 
carbon  film  is  thickest.  When  this  carbon  image  on  the 
copper  plate  is  dry  and  chlorid  of  iron  is  applied  to  it,  the 
iron  solution  penetrates  the  thinnest  parts  of  the  gelatin  resist 
first,  and  therefore  etches  the  plate  most  under  these  parts. 
Where  the  gelatin  resist  is  thickest,  corresponding  with  the 
high  light  of  the  positive,  the  iron  has  the  least  effect  on  the 
copper,  and  the  etching  is  slightest. 

We  will  consider  only  the  additional  information  a  carbon 
worker  must  possess  to  undertake  photogravure. 

THE  NEGATIVE  MOST  IMPORTANT. 

No  matter  which  method  of  photogravure  is  adopted  a 
perfect  photographic  negative  is  most  important.  Usually 
great  care  is  taken  in  its  retouching.  This  consists  not  only 
in  adding  shades  to  the  negative  by  working  over  the  var- 
nished film  with  soft  lead-pencils  but  in  removing  shades  by 
scraping  with  a  surgeon's  scalpel.  Gelatin  dry  plates  are 
almost  universally  used  in  making  photogravure  negatives. 
The  gelatin  film  being  too  slippery  to  hold  pencil-marks,  a 
few  drops  of  turpentine  are  rubbed  over  the  spot  to  be 


PHOTOGRAVURE 


53 


retouched  and  allowed  to  dry,  when  fine  grains  of  resin  are 
precipitated  by  evaporation  of  the  spirit,  giving  a  splendid 
"  tooth  "  for  holding  the  pencil  touches.  Should  there  not 
be  enough  grain  a  little  resin  is  added  to  the  turpentine. 
When  removing  shades  from  the  negative  the  scalpel  must 
be  kept  as  sharp  as  possible,  and  the  gelatin  film  scraped  away 
slowly  until  the  desired  shade  is  reached. 

A  REVERSED  TRANSPARENCY  REQUIRED. 

As  a  regular  studio  portrait  negative  is  frequently  sup- 
plied for  a  photogravure  plate,  reversed  negatives  will  not  be 
considered  here,  but  only  reversed  positives,  and  a  reversed 
positive  must  be  had  for  the  reason  that  the  negative  print 
from  it  on  carbon  tissue  is  printed  right.  This  tissue  is 
reversed  on  the  copper  printing-plate,  which  gives  an  etch  in 
reverse  on  the  copper,  and  consequently  the  proof  from  the 
copper  is  right. 

If  the  photogravure  is  to  be  a  different  size  from  the 
negative  furnished,  then  the  positive  must  be  made  in  the 
camera,  and  a  slow-working  dry  plate  had  better  be  used. 
Those  familiar  with  collodion  emulsion  can  make,  by  that 
method,  beautiful  transparencies  in  the  camera.  And  so  also 
can  perfect  transparencies  be  made  with  proper  collodion  and 
a  silver  bath. 

The  transparency  most  used  by  photogravure-makers  is 
secured  by  the  carbon  process  and  special  transparency  tissue 
is  supplied  for  that  purpose.  The  carbon  transparency  is 
made  on  a  glass  support,  and  can  be  retouched  more  easily 
than  the  negative.  It  can  be  vignetted,  skies  introduced,  and 
improved  in  many  ways  by  an  artist.  It  should  have  more 
contrast  than  required  in  the  photogravure  print.  Strips  of 
lantern-slide  binding-tape  should  be  pasted  on  the  back  of 
the  glass  to  mark  the  exact  dimensions  of  the  picture  required 
in  photogravure. 

THE  GR  A I N I N  G-BOX . 

The  principle  governing  the  graining  of  the  copper  plate 
is  this :  The  air  in  a  box  must  be  charged  with  fine  asphalt 
dust,  which  is  allowed  to  settle  on  the  plate  placed  near  the 


54 


HORGAN  S  HALF-TONE 


bottom  of  the  box.  The  longer  the  plate  is  allowed  to  remain 
the  greater  and  finer  the  quantity  of  dust.  Several  kinds  of 
graining-boxes  are  in  use.  Small  boxes  are  shaken  vigor- 
ously to  raise  the  cloud  of  dust.  Larger  boxes  are  mounted 
on  trunnions  and  revolve  several  times  before  coming  to  rest, 

while  the  most  satisfactory 
box  is  shown  in  the  diagram.  It 
should  be  several  inches  wider 
inside  than  the  largest  plate 
to  be  grained,  and  three  times 
the  height  of  the  width.  The 
bottom  is  rilled  completely 
with  a  square  zinc  funnel,  the 
bottom  of  which  connects  with 
an  air-pump  outside  of  the 
box.  The  top  of  the  box  is 
covered  with  fine  muslin  to 
allow  the  escape  of  the  air 
when  the  pump  is  at  work,  but 
at  the  same  time  confine  the 
asphalt  powder.  The  door  to 
the  box  is  just  over  the  top  of 
the  funnel,  and  the  plate  rest,  in  the  shape  of  an  open  frame, 
slides  on  cleats  at  the  sides  of  the  box. 


GRAINING  EOX. 


COPPER  AND  ITS  PREPARATION. 

The  copper  plates  had  better  be  purchased  polished  and 
beveled,  for  several  reasons.  The  dealer  has  selected  special 
metal  for  the  purpose,  and  he  has  the  machinery  and  tools 
for  properly  beveling  and  polishing.  There  is  too  great  a 
danger  of  scratching  a  valuable  plate  if  the  beveling  is  done 
after  the  etching.  Photogravure  copper  is  usually  softer 
than  that  used  by  relief-plate  engravers;  it  etches  readily 
and  is  usually  steel-faced  before  being  printed  from.  To 
free  the  copper  from  grease  it  must  be  heated  slightly  and 
placed  in  a  dish  containing  clean  potash  solution  for  a  few 
minutes.  It  is  then  rinsed  under  the  tap,  and  to  free  it  from 
stain  it  is  laid  in  a  dish  of  one-per-cent  sulphuric  acid  and 


PHOTOGRAVURE 


55 


swabbed  with  a  tuft  of  cotton.  Should  it  still  show  signs  of 
greasiness,  when  water  is  flowed  on  it,  then  go  over  the  cop- 
per with  whiting  wet  with  water  to  which  a  little  ammonia 
has  been  added.  Wash  the  plate  with  cotton  under  the  tap 
to  remove  all  traces  of  the  whiting.  Dry  the  plate  quickly, 
when  it  is  ready  for  the  asphalt  ground. 

GRAINING  THE  PLATE. 

Asphalt  finely  powdered  is  sold  for  this  special  purpose. 
Use  plenty  of  it  in  the  box  and  see  that  the  latter  as  well  as 
the  powder  is  perfectly  dry.  The  room  in  which  the  work  is 
being  done  should  be  free  from  drafts  that  might  disturb  the 
grain  on  the  plate  when  removed  from  the  box.  Practice 
laying  a  grain  or  ground  first  with  a  glass  plate.  Blow  up 
the  powder  in  the  box.  Wait  ten  seconds  for  the  coarsest 
grains  of  powder  to  subside.  Open  the  door  carefully  and 
slide  in  the  glass  plate ;  allow  it  to  remain  say  five  minutes 
and  examine  the  deposited  grain  with  a  magnifying  glass. 
Blow  up  the  powder  once  more,  wait  ten  seconds  and  insert 
another  plate  in  the  box  for  say  fifteen  minutes,  when  you 
will  find  the  grain  about  what  is  desired.  If  too  much  grain, 
give  less  time  in  the  box,  remembering*  that  you  can  always 
add  to  the  grain  deposit  by  placing  the  plate  in  the  box  again 
and  again  if  necessary.  Should  there  be  too  much  grain  on  a 
copper  plate  it  must  be  washed  off  completely  and  the  plate 
cleaned  and  grained  anew.  After  a  few  trials  the  precise 
time  to  elapse  between  blowing  up  the  powder  and  putting  in 
the  plate  and  allowing  the  plate  to  remain  in  the  box  to  get 
the  proper  ground  will  be  determined. 

When  the  proper  ground  is  secured  the  plate  is  held  with 
a  pair  of  pliers.  A  piece  of  blotter  between  the  upper  jaw  of 
the  pliers  and  the  copper  keeps  it  from  injuring  the  latter. 
The  plate  is  very  gently  laid  over  an  even  heat  until  the  color 
of  the  grain  changes  from  a  light  fawn  color  to  a  dark 
glossy  gray,  when  the  plate  is  allowed  to  cool. 

SENSITIZING  THE  TISSUE. 

With  the  carbon  tissue  comes  full  instructions  for  sensi- 
tizing, which  consists  in  cutting  a  piece  of  tissue  one-fourth 


56 


morgan's  half-tone 


inch  larger  each  way  than  the  size  of  the  engraved  surface. 
This  should  be  plunged  paper  side  down  into  a  bath  of  one 
ounce  of  bichromate  of  potash  to  twenty  to  thirty  ounces  of 
water  and  five  to  ten  drops  of  ammonia.  Air-bells  are 
brushed  from  the  gelatin  face  with  a  soft  camel's-hair  brush, 
then  the  air-bells  are  brushed  from  the  back.  The  tissue  will 
curl  at  first,  but  will  soon  flatten  out.  The  temperature  of  the 
bath  should  not  be  over  6o°  F.  In  three  minutes  the  tissue  is 
taken  out  and  laid  face  down  on  a  sheet  of  plate  glass  that 
has  been  previously  polished  with  talc,  or  a  clean,  glossy 
ferrotype  plate  can  be  used  in  place  of  the  plate  glass.  The 
surplus  water  is  pressed  out  from  between  the  gelatin  and 
the  glass  or  ferrotype  with  a  squeegee.  The  tissue  is  then 
dried  as  quickly  as  possible  without  melting  the  gelatin. 
When  dry  it  will  spring  from  the  plate  of  itself.  It  is  now 
sensitive  to  light  and  must  be  placed  behind  the  positive  in 
the  printing- frame  and  exposed  to  light.  Mark  on  the  back 
of  the  tissue  which  is  the  top  of  the  picture. 

TIMING  THE  EXPOSURE. 

Practice  will  be  the  only  guide  to  the  proper  exposure. 
But  the  strength  of  the  light  must  be  measured  with  an 
actinometer  such  as  carbonworkers  use  and  of  which  there 
are  many  different  patterns  on  the  market,  because  no  change 
is  visible  on  the  carbon.  After  exposure  the  film  is  taken 
from  the  printing-frame  and,  as  is  customary  with  even 
expert  operators,  this  first  print  is  used  for  trial  only  and  is 
developed  on  a  sheet  of  plate  glass.  If  the  exposure  is  found 
correct,  a  second  piece  of  tissue  is  exposed  exactly  as  the 
first  one  and  this  is  put  with  the  grained  copper  plate  in  a 
dish  of  cold  water,  the  air-bubbles  being  carefully  removed 
with  the  camel's-hair  brush.  When  the  tissue  begins  to 
flatten  out,  the  gelatin  tissue  is  brought  into  contact  with  the 
grained  plate,  care  being  taken  that  the  top  of  the  tissue  is 
on  the  top  of  the  plate.  Remove  both  from  the  water  and 
see  that  the  corners  of  the  tissue  register  with  the  pencil- 
marks  previously  made  on  the  plate,  then  squeegee  the  tissue 
securely  to  the  plate.    Blot  the  surplus  moisture  from  the 


PHOTOGRAVURE 


57 


back  of  the  plate  and  place  it  in  a  horizontal  position  for  ten 
or  fifteen  minutes  to  set. 

DEVELOPING  THE  IMAGE. 

After  the  tissue  has  set  put  it  in  a  deep  bath  of  water  of 
about  ioo°  to  no°  F.  In  a  few  seconds  the  layer  of  soluble 
gelatin  next  to  the  paper  backing  will  begin  to  soften,  when 
the  paper  can  be  gently  stripped  off  and  the  development 
of  the  negative  resist  begun.  The  light-hardened  gelatin 
being  in  contact  with  the  grain  will  remain,  while  the  un- 
hardened  gelatin  will  be  dissolved  by  the  water,  which  should 
not  be  heated  above  1200  F.  The  warm  water  can  be 
poured  from  a  pitcher  over  the  plate  and  local  development 
brought  about  by  regulating  the  height  of  the  falling  water 
or  the  continuance  of  the  stream  on  one  spot.  The  point  to 
be  observed  in  developing  is  that  the  thinnest  possible  layer 
of  gelatin  must  remain  upon  the  deepest  shadows  where  the 
film  will  be  thinnest.  All  soluble  gelatin  being  removed,  cold 
water  is  added  to  the  bath  so  as  to  reduce  the  temperature 
gradually,  and  the  plate  is  finally  washed  well  in  cold  water. 
It  is  then  whirled  to  get  rid  of  all  the  water  possible  and 
allowed  to  dry  spontaneously  without  using  heat,  in  a  place 
free  from  dirt.  To  hasten  the  drying,  the  plate  may  be 
flowed  with  water  and  alcohol  equal  parts,  gradually  increas- 
ing the  amount  of  alcohol  until  alcohol  alone  is  used.  It  can 
be  whirled  again  and  allowed  to  dry  slowly.  If  the  drying  is 
hurried,  the  resist  may  lift  from  the  plate.  When  dry,  the 
margins,  edges  and  back  of  the  plate  are  carefully  covered 
completely  with  either  an  asphalt  or  shellac  varnish,  and  the 
plate  is  ready  for  etching. 

ETCHING  SOLUTIONS  REQUIRED. 

Chlorid  of  iron  is  the  mordant  used  for  etching,  and  it 
has  this  peculiarity:  that  a  saturated  solution  will  scarcely 
penetrate  the  gelatin  resist,  while  the  more  it  is  diluted  with 
water  the  quicker  it  will  be  absorbed  by  the  gelatin  and 
reach  the  copper  plate.  Advantage  is  taken  of  this  property 
by  using  chlorid  of  iron  solutions  of  different  strengths. 


58 


HORGAN  S  HALF-TONE 


Chlorid  of  iron  is  purchased  at  40°  strength,  Baume's 
hydrometer,  at  a  temperature  of  700  F.  Four  other  solutions 
are  prepared  by  dilution  with  water  until  they  register  with  a 
Baume  hydrometer  380,  360,  340  and  320,  at  700  F.  The 
bottles  are  marked,  and  just  before  etching  five  dishes  are 
placed  side  by  side  and  sufficient  solutions  from  each  of  the 
bottles  poured  into  the  trays  to  more  than  cover  the  plate 
when  placed  in  it. 

ETCHING. 

The  copper  plate  with  the  gelatin  resist,  thoroughly  dry, 
is  first  laid  in  the  dish  containing  the  400  solution,  and  air- 
bells  brushed  from  the  surface  with  a  flat  camel's-hair  brush. 
The  tray  is  rocked  slightly,  and  it  will  be  noticed  that  the 
iron  is  beginning  to  attack  the  copper  in  the  deepest  shadows, 
or  where  the  resist  is  thinnest,  by  a  darkening  of  the  copper. 
The  time  for  etching  depends  on  the  subject,  the  resist  and 
the  temperature  of  the  solution,  so  rules  can  be  laid  down 
only  that  from  one  to  two  minutes  should  be  sufficient  for 
the  first  bath,  when  the  plate  is  transferred  to  the  380  bath 
for  a  less  time,  then  to  the  36°  bath,  and  so  on  until  the  dis- 
coloration of  the  plate  extends  to  the  thickest  part  of  the 
resist,  when  the  plate  is  at  once  plunged  into  a  bath  of  potash 
which  stops  the  action  of  the  mordant  and  softens  the  gela- 
tin resist  so  that  it  can  be  brushed  from  the  plate  and  the 
grain  ground  removed  with  turpentine  and  benzin. 

PROVING  AND  REETCHING. 

A  proof  can  now  be  pulled  from  the  plate,  and  if  it  should 
not  be  satisfactory  the  plate  may  be  cleaned  and  another  grain 
ground  laid  on  it  as  in  the  first  place,  and  by  stopping  out  the 
high  lights  and  reetching  shadows  or  backgrounds  the  plate 
may  be  darkened  wherever  desired.  Here  is  where  the  skill 
of  the  artist  is  required,  and  this  final  treatment  is  what  makes 
one  photogravure  superior  to  another.  It  would  be  just  as 
easy  to  tell  a  painter  how  to  lay  the  colors  on  his  canvas  as 
to  describe  the  reetching  of  a  photogravure. 

One  improvement  that  is  not  known  is  that  the  most 
expert  artist  in  photogravure  in  America,  at  this  stage, 


PHOTOGRAVURE 


59 


regrains  the  plate,  lays  an  enamel  ground  just  as  half-tone 
etchers  do,  and  with  the  same  solution ;  registers  the  positive 
again  perfectly  on  the  plate,  prints  through  the  enamel,  and 
without  burning-in  or  development  retches  the  plate  just  as 
he  wants  it ;  cleans  off  the  plate  for  a  proof,  and  if  he  thinks 
he  can  further  improve  it,  repeats  the  enamel  coating  and  the 
etching. 

This  is  the  last  word  in  photogravure. 

STEEL  ETCHING  AND  STEEL  FACING. 

MERCURY  MORDANT  FOR  STEEL. 

One  of  the  best  of  the  many  mordants  which  the  writer 
has  used  on  steel  is  the  following:  In  a  glazed  stoneware 
vessel  put  sixteen  ounces  of  water  and  add  powdered  bi- 
chlorid  of  mercury  and  one-fourth  ounce  of  powdered  alum. 
Put  the  vessel  over  heat  and  stir  with  a  glass  rod  until  a 
solution  is  had.  When  this  is  cool,  add  one  ounce  of  alco- 
hol and  the  mordant  is  ready  for  use. 

SPENCER  ACID  FOR  ETCHING  STEEL. 
The  secret  of  the  Spencer  acid  used  by  steel  engravers 


is  as  follows : 

A.  Nitric  acid,  C.  P  5  ounces 

Distilled  water  5  ounces 

Pure  metallic  silver  1  ounce 

B.  Nitric  acid,  CP  5  ounces 

Distilled  water   5  ounces 

Mercury  (quicksilver)   1  ounce 


After  making  these  two  solutions  separately,  mix  them 
and  keep  the  mixed  solution  in  a  glass-stoppered  bottle. 
When  using  it  can  be  diluted  one-half  with  distilled  water. 
When  a  little  of  this  solution  is  poured  upon  a  steel  plate 
there  is  no  action.  It  is  necessary  to  bend  a  strip  of  zinc 
so  that  one  end  comes  in  contact  with  the  bared  steel  and 
the  other  end  dips  into  the  Spencer  acid  on  the  steel ;  this 
generates  a  galvanic  action  which  starts  the  action  of  the 


GO 


horgan's  half-tone 


acid  immediately,  when  the  zinc  can  be  laid  aside  and  the 
liquid  continues  to  corrode  the  steel  until  it  is  exhausted. 
The  steel  engravers'  method  is  to  absorb  the  spent  acid 
with  blotter  and  pour  fresh  acid  on  the  steel. 

STEEL-FACING  COPPER  PLATES. 

Owing  to  the  large  editions  usually  required  from  deli- 
cate copper  photogravure  plates  it  is  customary  to  give  the 
printing  surface  a  protective  coating  of  a  film  of  iron  as 
thin  as  a  soap-bubble  though  as  hard  as  steel.  This  steel 
facing,  as  it  is  called,  had  better  be  done  by  an  electrotyper 
as  the  solution  from  which  the  iron  is  deposited  is  difficult 
to  keep  in  condition  when  used  but  seldom. 

The  outfit  for  steel  deposition  consists  of  a  depositing 
tank  with  its  solution,  an  iron  plate  for  an  anode  and  a 
small  dynamo  or  batteries.  It  is  better  to  consult  a  dealer 
in  electrotyping  supplies  for  advice  as  to  the  batteries  or 
dynamo,  who  will  be  guided  by  the  size  of  the  plates  and 
the  number  of  them. 

One  of  the  simplest  of  the  iron  depositing  solutions  is 
the  one  recommended  by  Mr.  Thomas  Huson  and  is  as 
follows : 

Water   40  ounces 

Chlorid  of  ammonium   2  ounces 

Double  sulphate  of  iron  and  ammonia   1  ounce 

Protosulphate  of  iron   1  ounce 

The  salts  are  to  be  dissolved  in  the  water  and  the  solu- 
tion filtered  just  before  use.  The  important  feature  of 
this  work  is  to  get  the  surface  of  the  copper  absolutely 
clean  with  whiting  and  water  in  order  that  the  iron  film 
will  be  evenly  deposited.  The  deposition  should  not  take 
more  than  fifteen  minutes,  and  to  keep  the  steel  facing 
from  rust  it  must  be  kept  covered  with  oil  or  beeswax. 


SWELLED  GELATIN  ENGRAVING. 
Moss  Engraving  Company,  about  1883. 


THE  MOSS  PROCESS, 

KNOWN  AS 

THE  SWELLED  GELATIN  RELIEF  PROCESS,  THE  FIRST 
PRACTICAL  PHOTO-RELIEF  PROCESS. 


It  was  in  1871-72  that  John  Moss  worked  out  in  New 
York  the  first  practical  photoengraving  process.  He  per- 
formed certain  portions  of  the  process  in  secret  and  sup- 
posed that  his  secrets  died  with  him.  His  methods  have 
never  been  published,  but  as  the  writer  was  experimenting 
on  similar  lines  ten  years  later,  and  obtained  good  results 
eventually,  it  is  safe  to  assume  that  the  Moss  process  was 
about  as  follows : 

A  gelatin  solution  was  made  up  daily  in  the  following 
proportions : 

Cox's  gelatin    1  ounce 

Water    12  ounces 

Bichromate  of  potash  120  grains 

The  gelatin  is  allowed  to  swell  in  the  water  and  is  then 
heated  to  1200  F.,  when  the  gelatin  dissolves  and  the 
bichromate,  in  a  finely  powdered  form,  is  stirred  in.  The 
solution  is  kept  at  this  temperature  until  it  is  filtered  and 
then  poured  on  leveled  pieces  of  plate  glass  which  have  had 
their  surfaces  ground  with  fine  emery.  The  object  of  this 
grinding  is  to  prevent  the  gelatin  drying  and  lifting  off  the 
surface  of  the  plate  glass,  which  it  will  do  if  the  surface  is 
not  ground. 

DRYING,  PRINTING  AND  SWELLING. 

The  gelatin-coated  pieces  of  plate  glass,  as  soon  as  the 
gelatin  sets,  are  put  in  a  closet  in  which  a  current  of  air 
dries  them  in  a  few  hours.  Then  they  are  printed  under  a 
most  intense  negative  in  sunlight  at  the  end  of  a  long  box 
that  will  only  permit  the  light  to  reach  them  vertically,  so 
as  to  print  straight  down  to  the  back  of  the  gelatin  film. 
When  the  gelatin  is  so  printed  it  is  removed  from  the  pres- 
sure frame  and  placed  to  swell  in  cold  water.    The  gelatin 

61 


62 


horgan's  half-tone 


hardened  by  the  action  of  light  does  not  absorb  water,  while 
the  unacted-upon  gelatin  does,  thus  giving  an  image  in  slight 
relief.  The  swelled  gelatin  is  then  hardened  by  placing  in  a 
saturated  solution  of  sulphate  of  iron,  after  which  it  is 
fanned  partially  dry  and  flowed  over  with  a  solution  of 
asphalt  in  a  mixture  of  ether  and  bisulphid  of  carbon. 
These  solvents  quickly  evaporate,  though  hot  wax  may  be 
poured  over  the  asphalt  coating  immediately  and  a  block 
of  wax  built  up  as  thick  as  necessary.  The  whole  is  put 
into  a  vessel  of  cold  water,  when  the  wax  with  its  asphalt 
surface  strips  easily  from  the  swelled  gelatin. 

If  this  asphalt-coated  wax  block  could  be  printed  from 
at  once  the  process  would  be  perfect,  though  the  plate  would 
be  a  trifle  shallow.  A  metal  printing-plate  must  be  had, 
and  this  is  done  by  making  a  mold  in  plaster  of  paris,  and 
when  this  latter  mold  is  dry,  casting  a  stereotype,  which  is 
the  printing-plate. 

Some  of  the  peculiarities  of  this  process  are  these:  In 
the  first  place,  when  the  swelling  takes  place  in  the  gelatin 
the  tendency  is  to  "  cup  "  the  sunken  line  which  is  later 
the  printing  surface.  Each  succeeding  mold  and  cast  has 
a  tendency  to  further  round  the  printing  surface  so  that 
the  stereotyped  relief  line  has  a  decided  convex  surface. 
This  was  taken  advantage  of  by  the  printers  who  used  the 
plates,  because  the  lighter  the  pressure  the  thinner  the  lines 
in  the  impression;  while  to  thicken  the  line,  all  that  was 
needed  was  to  increase  the  overlay  and  more  of  the  convex 
surface  was  impressed  on  the  paper. 

Another  peculiarity,  which  was  a  drawback,  was  that 
the  thinner  the  gelatin  film  the  better  the  result,  but  the 
shallower  the  plate  and  the  more  work  for  the  engraver  to 
lower  the  shallow  surfaces  between  the  printing  lines. 
Some  of  Moss'  earliest  plates  required  engraving  between 
almost  every  line. 


PHOTO-ELECTROTYPE. 
By  Photo-Electrotype  Engraving  Company,  about  1885. 


THE  PHOTOELEGTROTYPE  PROCESS, 

COMMONLY 

TERMED  THE  "  WASH-OUT  "  PROCESS  IN  AMERICA  AND 
LEIMTYPE  IN  GERMANY. 


The  photoelectrotype  process  was  one  that  about  1880 
produced  the  best  photoengravings,  and  it  did  not  seem  that 
it  could  be  superseded.  It  is  now  only  a  memory,  and  but 
few  of  the  old  engravers  are  left  to  tell  of  the  procedure. 

It  was  the  method  used  to  reproduce,  among  other  books, 
the  entire  Encyclopedia  Britannica,  and  also  a  Webster's 
Unabridged  Dictionary.  The  publication  of  those  works 
alarmed  compositors,  who  feared  that  the  reproduction  of 
standard  works,  in  any  size,  by  this  photomechanical  process 
would  bring  ruin  to  the  typesetter  and  some  publishers. 

As  this  slow  method  of  engraving  has  some  good  quali- 
ties it  is  liable  to  be  rediscovered,  as  so  many  photo  processes 
are,  so  a  brief  resume  of  the  process  is  given  here. 

The  most  successful  method  may  be  said  to  have  orig- 
inated with  William  Mumler,  of  Boston,  who  obtained  a 
patent  on  it  May  18,  1875.  The  invention  has  frequently 
been  credited  to  J.  Husnik,  of  Prague,  who  received  a 
British  patent  on  January  1,  1887,  twelve  years  after 
Mumler  was  successfully  working  the  same  process  in  the 
United  States.    Husnik  called  his  invention  "  leimtype." 

The  principle  of  the  process  lies  in  the  destruction  of  the 
swelling  property  in  gelatin ;  sensitizing  this  gelatin  with  a 
bichromate  and  flowing  it  over  a  level  surface  so  that  it 
may  dry  into  sheets  about  one-sixteenth  of  an  inch  thick; 
exposing  one  of  these  sheets  under  an  intense  negative  until 
the  light  hardens  the  gelatin  film  through  to  the  back.  The 
exposed  film  is  then  secured  with  shellac  or  gutta-percha 
to  a  zinc  support,  and  the  gelatin  unhardened  by  light  is 
washed  out  with  a  brush  and  an  alkaline  solution  from 
between  the  light-hardened  lines  of  the  image,  hence  the 
name,  "  the  wash-out  process."  After  this  washed-out  film 
is  dried  it  can  be  printed  from  direct  or  an  electrotype  plate 

63 


64 


horgan's  half-tone 


made  from  it.  This  was  called  the  single  wash-out  process, 
to  distinguish  it  from  Mumlers  and  Husnik's  methods. 

It  might  be  said  of  Mumler,  in  passing,  that  he  was 
also  the  originator  of  the  spirit-photography  humbug  that 
fooled  Horace  Greeley  and  many  scientists  at  the  time,  and 
when  revived,  as  it  is  occasionally,  continues  to  deceive 
apparently  intelligent  people. 

DOUBLE  WASH-OUT  PROCESS. 

Mumler  and  Husnik  both  found  it  difficult  to  get  the 
strongest  sunlight  to  penetrate  through  to  the  back  of  the 
film  without  lateral  action,  so  they  both  hit  on  similar 
methods  to  overcome  this  undercutting  of  the  light  rays. 
Mumler,  after  washing  out  the  exposed  film  the  first  time, 
filled  in  the  sunken  portions,  where  the  unhardened  gelatin 
had  been  removed,  with  a  black  paste  something  the  nature 
of  shoe  blacking.  Then  the  film  was  exposed  to  light  for 
a  longer  period  than  the  first  time,  the  black  paste  washed 
away  and  the  underexposed  gelatin  under  it.  From  this 
second  washing  it  was  called  the  "  double  wash-out  process." 
Husnik,  instead  of  rubbing  in  the  black  as  Mumler  did, 
and  then  wiping  the  surface  clean  as  a  card  plate  printer 
does,  painted  black  in  between  the  lines  with  a  fine  hair 
pencil. 

One  of  the  disagreeable  features  of  this  process  was  the 
offensive  odor  of  the  gelatin  when  fit  for  use.  It  was  lit- 
erally, what  the  workmen  termed  it,  "  rotten.''  And  this 
"  rotting,"  as  it  was  called,  was  produced  by  long  "  cook- 
ing "  at  a  temperature  of  from  1200  to  1500  F.  The  time 
required  being  from  fifteen  to  forty-eight  hours,  and  the 
proper  amount  of  cooking  was  determined  when  the  odor 
reached  its  most  offensive  stage. 

COMPOSITION  OF  WASH-OUT  GELATIN. 

It  is  probable  if  the  photoelectrotype  process  were  in  use 
to-day  that  a  common  glue  combined  with  fish  glue  would 
be  used  instead  of  the  gelatin  and  albumen  formerly  thought 


THE  PHOTOELECTROTYPE  PROCESS 


65 


necessary.  The  formula  given  here  is  as  simple  a  one  as 
was  found  practicable : 

Nelson's  No.   2,   or  Cooper's  common 


The  gelatin  is  put  into  the  ten  ounces  of  water  and 
allowed  to  soak  up  the  water.  It  is  then  put  into  a  double 
cooker  with  an  outside  vessel  of  hot  water  so  regulated  that 
the  temperature  shall  range  about  1300  to  1400  F.  After 
twenty-four  hours  of  this  temperature  the  gelatin  should 
have  lost  all  its  swelling  property.  While  the  rotted  gelatin 
is  still  hot,  add  the  120  grains  of  potassium  bichromate  in 
a  finely  powdered  state,  stirring  the  gelatin  at  the  same  time. 
Add  the  thirty  minims  of  ammonia,  then  the  one  ounce  two 
drams  of  glycerin  and  the  white  of  one  egg ;  filter  through 
muslin. 

Care  must  be  taken  in  the  amount  of  glycerin  used,  for 
the  more  glycerin  the  easier  the  light-hardened  gelatin  can 
be  washed  away,  while  too  little  glycerin  will  leave  the  film 
brittle. 


The  gelatin  is  then  molded  into  sheets  by  using  cases 
similar  to  those  used  by  an  electrotyper  for  wax,  except 
that  the  bottom  of  the  photoelectrotyper's  case  is  made  of 
plate  glass  surrounded  with  a  wooden  frame,  beveled  out- 
ward and  about  an  inch  deep.  The  plate  glass  on  the  bot- 
tom of  the  cases  is  waxed  and  the  cases  laid  on  a  level  table, 
when  the  gelatin,  just  warm  enough  to  be  in  solution,  is 
poured  in  to  the  depth  of  about  half  an  inch.  When  the  gel- 
atin is  jellied  so  that  the  cases  can  be  moved  without  injury 
to  the  gelatin  they  are  put  into  a  drying-room  where  filtered 
dry  air  is  drawn  through  by  any  convenient  means.  The 
gelatin  in  the  cases  should  give  up  its  moisture  in  two  days. 


gelatin   

Water  

Potassium  bichromate 

Water  ammonia   

Glycerin  

Albumen   


120  grains 
30  minims 
1  ounce  2  drams 


10  ounces 


4  ounces 


1  ounce 


MAKING  THE  SHEETS. 


5 


66 


horgan's  half-tone 


though  if  it  requires  three  days  it  will  not  injure  the  films. 
When  they  are  dry  they  strip  easily  from  the  case  and  are 
ready  for  exposure  to  light  in  a  printing- frame. 

PRINTING  THE  IMAGE  AND  WASHING  OUT. 

The  reversed  negative  must  be  as  opaque  as  it  is  possible 
to  make  it,  while  the  transparent  image  must  be  absolutely 
so.  The  smooth  side  of  the  film  is  placed  next  to  the  nega- 
tive film  in  the  printing- frame  and  the  exposure  made  to 
sunlight  at  the  end  of  a  box  from  three  to  six  feet  long, 
depending  on  the  size  of  the  printing-frame.  The  object 
of  this  box  is  to  permit  only  light  rays  to  penetrate  the  film 
at  exact  right  angles.  After  an  exposure  of,  say,  ten  min- 
utes to  sunlight,  the  frame  is  taken  into  the  darkroom. 
Should  the  gelatin  show  a  tendency  to  stick  to  the  negative, 
this  may  be  overcome  by  rubbing  the  negative  film  with  talc 
and  the  gelatin  film  as  well. 

The  brushes  used  to  wash  out  the  unexposed  gelatin 
between  the  lines  can  be  fine  bristle  clothes-brushes.  The 
principle  is  that  a  broad  brush  having  a  good  surface  area 
will  not  permit  the  bristles  to  sink  too  far  below  the  surface, 
though  narrow  brushes  are  preferred  by  skilled  workers. 
Three  trays  are  necessary  —  one  for  hot  water,  another  for 
cold  water,  and  the  third  for  wood  alcohol.  In  the  cold 
water  tray  is  laid  a  sheet  of  glass.  The  exposed  gelatin 
film  is  drawn  through  the  same  tray  of  cold  water,  face  up, 
and  as  soon  as  it  is  over  the  glass  plate  both  are  drawn  out 
of  the  water  quickly  and  the  gelatin  film  squeegeed  to  the 
glass,  to  which  it  quickly  adheres  by  suction.  The  brush 
is  first  dipped  in  the  alcohol  and  the  surface  of  the  gelatin 
cleaned  of  talc  and  any  possible  grease ;  the  brush  is  dipped 
in  the  hot  water  and  the  surface  of  the  gelatin  scrubbed 
briskly  with  it,  being  sure  to  go  over  the  whole  surface 
evenly.  It  is  best  to  use  a  circular  motion  with  the  brush. 
Almost  immediately  the  design  will  show  in  slight  relief. 
When  it  has  been  washed  out  sufficiently  give  the  plate  a 
quick  rinse  under  the  tap;  with  a  palette-knife  strip  the 
film  from  its  glass  support  and  plunge  it  quickly  into  the 


THE  PHOTOELECTROTYPE  PROCESS 


67 


wood  alcohol,  where  it  becomes  milky  in  appearance.  The 
alcohol  absorbs  the  water  from  the  gelatin  in  about  fifteen 
to  twenty  minutes,  when  the  film  is  taken  out  and  either 
put  in  the  drying-room  or  fanned  dry. 

THE  SECOND  WASH-OUT. 

When  the  film  is  dry  it  will  be  found  that  the  relief  is 
not  quite  sufficient  for  an  electrotype,  so  the  washed-out 
parts  are  filled  in  with  a  good  shoe  blacking  and  the  surface 
polished  off  just  as  a  copper-plate  printer  handles  a  steel 
or  copper  plate.  In  fact,  it  is  likely  that  plate  printing-ink 
and  a  polish  with  powdered  magnesia  would  answer  admir- 
ably. The  plate  is  again  exposed  to  light  in  the  printing- 
frame  under  a  sheet  of  clear  glass  and  at  the  end  of  the 
long  box  for,  say,  twenty  minutes,  when  it  is  removed  from 
the  frame,  and,  with  thick  shellac,  attached  to  a  glass  or 
metal  support.  A  brush  is  dipped  in  the  wood  alcohol  and 
the  blacking  loosened  from  between  the  lines.  Then  the 
film  is  scrubbed  vigorously  with  a  brush  and  hot  water  until 
sufficient  relief  is  had,  when  it  is  rinsed  and  quickly 
plunged  into  the  alcohol  to  stop  the  softening  action  of  the 
water  on  the  film.  The  alcohol  loosens  the  shellac  so  that 
the  film  is  easily  removed  and  dried,  when  it  is  attached  to 
its  final  zinc  support  with  shellac. 

A  proof  is  pulled  from  the  plate  and  any  blemisftes 
engraved  out  of  it,  and  then  it  is  turned  over  to  the  electro- 
typer.  In  case  of  any  line  or  dot  being  lost  in  the  wash-out 
gelatin  the  electrotype-finisher  will  punch  up  the  plate  from 
the  back  and  supply  it. 

The  shellac  used  to  secure  the  gelatin  film  to  its  supports 
is  merely  shellac  that  has  been  soaked  in  alcohol  until  it 
becomes  a  thick  paste  which  is  softened  by  heat  before  using. 
For  a  temporary  support  use  a  smooth  sheet  of  zinc,  from 
which  the  film  can  easily  be  removed  later  by  the  use  of  a 
sharp  palette-knife  between  the  shellac  and  the  zinc,  when 
the  film  will  split  off. 

For  a  permanent  support  the  surface  of  the  zinc  is 
roughened  with  sandpaper  to  which  the  shellac  adheres 


68 


HORGAN  S  HALF-TONE 


firmly.  Rubber,  gutta-percha  and  even  strong  glue  have 
been  used  to  secure  the  gelatin-relief  film  to  its  support. 

Large  editions  have  been  printed  from  the  original  gela- 
tin film  without  electrotyping.  The  gelatin  was,  however, 
after  washing  out  and  dried,  either  exposed  to  light  from 
the  back  for  a  long  time  or  hardened  with  a  bath  of  chrome 
alum.  It  was  also  the  custom  with  some  operators  to  expose 
the  back  of  the  film  to  light  for  a  short  time  before  the  first 
wash-out. 

It  was  said  of  the  washed-out  films  that  they  could  be 
filed  away  for  use  at  any  time.  Such  films  in  the  writers' 
possession  for  twenty-five  or  thirty  years  are  even  more 
brittle  than  if  they  were  glass,  due  possibly  to  the  continuing 
action  of  the  bichromate  left  in  the  film  and  the  evaporation 
of  the  glycerin. 


LINE  ENGRAVING. 
Globe  Engraving  &  Electrotype  Co.,  Chicago. 


RELIEF-LINE  ENGRAVING. 


WHICH  IS 

THE  MOST  IMPORTANT  OF  ALL  THE  PHOTOMECHAN- 
ICAL ENGRAVING  PROCESSES. 


The  engraving  of  drawings  in  lines,  or  the  reproduction 
of  type  by  photoengraving,  comprises  the  greater  part  of 
processwork  the  world  over,  and  still  the  complaint  can  be 
justly  made  that  in  most  cases  either  no  improvement  has 
been  made  in  this  class  of  engraving  or  frequently  the  quality 
of  the  work  has  deteriorated. 

The  causes  for  the  deterioration  can  be  briefly  stated. 
Line  engraving,  and  particularly  the  reproduction  of  type, 
requires  even  greater  skill  on  the  part  of  the  workmen  than 
half-tone  engraving,  and  still  the  charge  for  the  work  usually 
does  not  pay  the  cost  of  producing  it  properly,  consequently 
the  work  is  slighted.  Then  the  same  collodion  is  used  for 
line-negative  making  that  is  used  for  half-tone  negatives, 
which  should  not  be  done.  And  worst  of  all,  the  line  opera- 
tor uses  "  cutting  "  solution  on  the  negative  which  destroys 
the  character  of  the  copy.  To  prove  the  last  charge,  exam- 
ine a  negative  of  a  line  subject  that  has  been  "  cut  "  wherever 
two  lines  cross,  and  notice  how  the  sharp  corners  have  been 
dissolved  away,  never  to  be  restored  by  any  succeeding 
operation. 

SPECIAL  LINE  COLLODION. 

The  collodion  used  for  line  engraving  should  be  a  more 
contrasty  one  than  that  used  for  half-tone  negatives,  and 
therefore  should  contain  but  little  bromid  salt.  The  sensi- 
tiveness of  the  iodids  was  found  by  the  writer  to  be  about  in 
the  following  order:  Iodic!  of  zinc  makes  the  most  sensitive 
collodion,  followed  by  white  iodid  of  ammonium,  and  then 
cadmium,  potassium,  sodium,  and  least  sensitive  was  iodid 
of  uranium.  Iodid  of  uranium  gives  the  greatest  intensity 
and  so  do  the  iodids  of  zinc  and  potassium ;  but  they  seem 

69 


70 


horgan's  half-tone 


to  put  the  silver  bath  out  of  working  condition  quicker  than 
the  iodids  of  ammonium  and  sodium,  so  that  a  reliable  work- 
ing formula  for  line  collodion  was  found  to  be  the  following : 


Ether,  sulphuric,  U.  S.  P.,  specific  gravity  0.725..    5  ounces 


Collodion  preparation  is  an  exceedingly  simple  operation 
if  the  following  method  is  adopted:  Take  equal  quantities 
of  ether  and  alcohol.  For  every  ounce  of  the  total  quantity 
of  these  liquids  weigh  out  7  grains  of  guncotton,  6  grains  of 
brown  iodid  of  ammonium,  and  1  grain  of  bromid  of  cad- 
mium. Put  the  cotton  to  soak  in  the  ether,  dissolve  the  salts 
in  the  alcohol,  and  then  pour  the  alcohol  into  the  ether,  when 
the  cotton  will  dissolve.  Shake  well  and  allow  it  to  "  ripen  " 
in  a  cool,  dark  place  for  a  couple  of  days.  Filter  well 
through  absorbent  cotton  before  use. 


In  winter  five  per  cent  less  alcohol  and  five  per  cent  more 
ether  can  be  used  to  advantage,  though  as  the  workroom 
should  be  maintained  at  as  near  60  degrees  as  possible,  in 
winter  it  is  not  necessary  to  change  the  proportions  of  the 
ether  and  alcohol  from  the  normal.  As  the  ether  evaporates 
first,  when  collodion  becomes  too  thick  more  ether  than  alco- 
hol should  be  added  to  dilute  it.  An  excess  of  ether  closes  the 
pores  in  the  film  so  that  the  silver  salt  does  not  penetrate  so 
well,  while  an  excess  of  alcohol  makes  the  film  too  porous 
and  rotten,  causing  it  to  tear  easily  under  the  tap  when  wash- 
ing. Collodion  as  recommended  above  should  be  made  up 
at  least  once  a  week,  and  some  of  the  old  and  the  new  mixed 
before  filtering  to  make  the  best  working  collodion. 

There  are  at  least  fifty-seven  different  varieties  of  collo- 
dion in  use,  each  operator  having  his  pet  formula,  but  the 
fewer  the  ingredients  the  less  complications  occur  in  taking 


FORMULA  FOR  LINE  COLLODION. 


Alcohol,  ethylic,  95  per  cent 
Iodid  of  ammonium,  brown 

Bromid  of  cadmium  

Guncotton  (pyroxylin)   


5  ounces 
60  grains 
10  grains 
70  grains 


POINTS  ABOUT  COLLODION. 


RELIEF-LINE  ENGRAVING 


71 


care  of  the  silver  bath  and  the  intensification  of  the  negative 
which  follows.  Too  much  insistence  can  not  be  laid  on  using 
a  proper  collodion  bottle.  One  with  a  glass  cap  that  covers 
the  entire  top  of  the  bottle,  preventing  dust  and  evaporation, 
and  which  has  besides  a  wide  base  with  a  recess  to  hold  sedi- 
ment, is  the  ideal  pouring  bottle  for  collodion.  For  further 
points  see  "  Collodion  for  Photolithography  "  in  this  book. 

RELIEF  AND  PHOTOLITHOGRAPHIC  NEGATIVES. 

All  that  has  been  advised  in  making  negatives  for  photo- 
lithography in  the  chapter  on  that  subject  applies  to  negatives 
for  engraving  lines  in  relief  in  the  matter  of  cleaning  glass, 
also  to  the  substratum  and  developer  used,  only  that  a  slight 
change  is  suggested  in  the  collodion,  and  it  is  recommended 
that  the  silver  bath  be  stronger.  A  45-grain  bath  will  be 
found  an  improvement  for  line  negatives.  Greater  intensity 
is  required  in  negatives  for  relief  engraving,  and  as  they 
require  always  to  be  reversed,  information  regarding  these 
operations  follow. 

INTENSIFICATION. 

Intensification  means  the  increasing  of  the  deposit  on  a 
negative  so  as  to  augment  its  opacity  without  staining  the 
transparent  parts  of  the  collodion  film  representing  the  lines 
or  dots  of  the  copy.  It  is  a  purely  chemical  reaction,  so  that 
the  chemicals  and  their  application  should  be  used  with  intel- 
ligence. Besides  the  intensifies  recommended  in  the  chapter 
on  negative-making  for  photolithography,  and  which  can  be 
used  for  relief-line  negatives,  the  following  intensifier  is 
preferred  for  the  present  purpose,  owing  to  the  extreme 
opacity  of  negative  produced  by  it : 

Copper  sulphate    2  ounces 

Potassium  bromid    1  ounce 

Water,  pure  or  distilled   20  ounces 


When  the  chemicals  are  completely  dissolved  in  the  water 
the  solution  can  be  flowed  on  the  negative  that  has  been 
previously  fixed  with  cyanid  of  potassium  solution  and  well 


72 


horgan's  half-tone 


washed.  In  a  short  time  the  image  begins  to  change  to  a 
creamy  white  in  color,  and  when  this  color  has  completely 
penetrated  to  the  back  of  the  film  the  plate  is  well  washed 
under  the  tap  and  flowed  with 

Silver  nitrate   i  ounce 

Water,  distilled    20  ounces 

Citric  acid  enough  to  make  solution  acid. 

After  which  the  film  is  again  washed.  The  image  is  now  a 
deep  brown-black  in  color,  which  will  be  found  opaque 
enough  for  most  purposes.  To  render  the  film  an  intense 
black  the  operation  may  be  repeated.  Other  intensifies  may 
be  found  by  consulting  the  index. 

STRIPPING  AND  REVERSING  THE  NEGATIVE  FILM. 

When  the  negative  is  perfectly  dry,  which  is  usually  done 
in  a  heated  oven,  it  is  cooled  on  an  iron  slab  or  with  an  elec- 
tric fan  and  flowed  with  the  following  rubber  solution : 

Pure  Para  rubber,  cut  into  shreds   1  ounce 

Benzin  or  benzol   1  quart 

The  rubber  is  allowed  to  soak  in  the  solvent  which  can  be 
either  benzol  or  the  cheaper  benzin  until  it  will,  upon  shaking, 
give  a  solution  about  the  consistency  of  collodion.  There  is 
little  danger  of  having  this  rubber  film  too  thin ;  the  error  is 
usually  in  having  it  too  thick.  It  should  be  flowed  on  and 
off  the  negative  quickly,  so  as  not  to  get  too  thick  a  film.  It 
is  allowed  to  dry  spontaneously  until  the  benzin  solvent 
evaporates,  which  it  does  quickly.  When  the  rubber  is  firm 
to  the  touch  of  the  finger  it  is  dry  and  can  be  flowed  with 
plain  collodion  made  up  as  follows : 

Ether,  sulphuric    10  ounces 

Alcohol,  95  per  cent   10  ounces 

Guncotton  (pyroxylin)   120  grains 

Castor  oil    40  minims 

Though  the  above  formula  for  stripping  collodion  is  the 
one  the  writer  uses,  it  should  be  remembered  that  there  is 
great  latitude  in  the  proportions  of  the  cotton  and  castor  oil. 


RELIEF-LINE  ENGRAVING 


73 


After  ether  and  alcohol  are  mixed  in  equal  proportions  meas- 
ure the  number  of  ounces,  and  if  cotton  is  added  in  any  pro- 
portion of  from  5  grains  to  10  grains  to  the  ounce  of  the 
combined  ether  and  alcohol  and  from  to  3  minims  of 
castor  oil  is  used,  any  of  these  proportions  will  make  a  good 
working  stripping  collodion,  the  only  difference  being  that 
the  film  is  thicker  as  the  quantity  of  cotton  is  increased.  The 
proportion  of  castor  oil  should  be  increased  with  the  increase 
in  the  cotton. 

The  collodion  film  can  be  dried  over  heat;  in  fact,  on 
newspapers,  where  speed  in  the  operations  is  an  important 
factor,  it  is  customary  to  set  fire  to  the  collodion  film  as  soon 
as  it  is  set.  This  burns  off  the  ether  and  alcohol  almost 
immediately. 

DETACHING  THE  FILM  FROM  ITS  GLASS  SUPPORT. 

The  negative  film  is  now  cut  with  a  sharp-pointed  knife 
just  outside  the  image  so  that  it  will  occupy  as  little  space  as 
possible  when  a  number  of  negatives  are  stripped  and  turned 
upon  the  same  sheet  of  glass.  In  the  case  of  "  layouts  "  or 
borders  where  several  half-tones  are  to  be  inserted  in  a  single 
frame  or  border  it  is  customary  to  cut  out  the  openings  in  the 
frame  or  layout  after  the  film  is  turned  upon  its  final  support. 

To  detach  the  collodion  film  from  its  original  glass  sup- 
port it  is  necessary  to  destroy  the  albumen  substratum  that 
has  thus  far  held  it  secure  to  the  glass.  This  is  done  by 
placing  the  glasses  holding  the  negative  films  to  be  stripped 
in  a  tray  containing 

Water    10  ounces 

Acetic  acid  (30  to  36  per  cent)   1  ounce 

For  hurried  newspaper  work  the  acetic  acid  can  be 
increased  until  it  is  one-half  the  quantity  of  the  solution. 
This  solution  will  work  more  rapidly  when  heated.  In  from 
three  to  five  minutes  the  acetic  acid  will  have  penetrated 
through  the  rubber  and  collodion  films  and  have  destroyed 
the  film  of  albumen  so  that  the  negative  film  will  be  loose 
upon  its  glass  support.    When  this  is  so,  the  acetic  acid  is 


74 


HORGAN'S  HALF-TO*NE 


washed  from  the  negative  and  a  corner  of  the  negative  film 
is  raised  from  the  glass  with  the  point  of  a  knife-blade,  and 
then  two  corners  are  taken  hold  of  and  the  whole  film  slowly 
stripped  from  the  glass  and  carefully  laid  down  reversed 
upon  its  final  crystal-plate  glass  support,  which  is  lying  on  a 
level  support,  and  flooded  with  clean  water  so  that  the 
stripped  film  may  be  floated  into  its  proper  position. 

Most  negative-turners,  as  the  men  who  strip  films  are 
called,  prefer  that  the  final  crystal-plate  glass  support  be  laid 
on  a  ground  glass  fixed  at  an  angle  like  a  retoucher's  stand 
with  a  light  behind.  One  advantage  of  this  is  that  particles 
of  grit  or  dirt  are  more  easily  washed  down  from  the  glass, 
and  are  not  held  under  the  transferred  film.  To  squeegee  the 
water  out  from  between  the  film  and  the  glass  it  is  best  to  use 
pieces  of  lintless  blotter  cut  into  squares  of  2  by  3  inches. 
This  blotter  absorbs  the  water  and  does  not  scratch  the  film. 
After  the  film  or  films  are  turned  and  squeegeed  fast  to  the 
glass  it  is  allowed  to  dry. 

PREPARATION  OF  THE  METAL. 

For  line  engraving  we  will  only  consider  the  use  of  zinc. 
This  metal  had  better  be  purchased  ground  and  polished.  It 
contains  some  grease  which  is  removed  by  placing  the  metal 
in  a  strong  solution  of  caustic  potash  or  lye  for  a  few  min- 
utes, washing  off  the  potash  and  then  removing  the  polished 
surface,  containing  the  grease,  with  the  end  of  a  piece  of 
engravers'  charcoal.  Instead  of  the  charcoal  fine  pumice 
powder  may  be  applied  with  a  brush  or  a  felt  pad.  All  the 
grinding  of  the  surface  must  be  done  with  water. 

In  Europe  it  is  customary  to  give  the  surface  of  the  zinc 
a  matt  surface  with  what  is  called  a 

GRAINING  BATH. 

This  bath  is  composed  of  water  in  which  is  a  trace  of 
nitric  acid  and  some  powdered  alum.   The  proportion  of  the 


RELIEF-LINE  ENGRAVING  75 

components  of  this  bath  has  a  wide  range,  though  the  fol- 
lowing will  be  found  to  work  well : 

Water    V2  gallon 

Nitric  acid   1  ounce 

Alum,  powdered    3  ounces 


This  graining  bath  is  used  in  a  tray  in  which  the  zinc  plate 
is  laid  and  the  graining  solution  allowed  to  flow  back  and 
forth  over  the  plate  in  order  to  dislodge  the  gas  bubbles  that 
form.  These  bubbles  can  be  removed  with  a  flat  bristle 
etching-brush.  When  the  plate  receives  an  even  gray  matt 
surface  all  over,  it  is  removed  and  washed  well  under  the  tap 
with  a  clean  sponge  or  tuft  of  cotton,  and  it  is  ready  for 
sensitizing. 

SENSITIZING  SOLUTION  FOR  ZINC. 

In  the  whole  list  of  substances  known  to  photographic 
chemists  as  being  sensitive  to  light  there  is  probably  none  as 
simple,  yet  delicate  and  effective,  as  albumen  containing  a 
bichromate.  A  film  of  it  can  be  produced  as  thin  almost  as 
a  soap  bubble  on  a  sheet  of  metal  and  still  be  utilized.  It  is 
the  most  used,  least  appreciated  and  most  abused  sensitizer  in 
the  photomechanical  printing  processes.  The  following  is 
one  method  of  preparing  it  properly.   The  ingredients  being 


Water,  distilled    8  ounces 

Albumen,  fresh  egg   1  ounce 

Bichromate  ammonia   20  grains 

Ammonia  water,  26 0   8  drops 


The  albumen  of  a  fresh  egg  should  be  beaten  with  a  clean 
eggbeater  until  it  becomes  froth.  This  is  allowed  to  settle, 
when  it  should  make  one  ounce.  Four  ounces  of  the  distilled 
water  is  stirred  into  the  albumen  and  the  bichromate  of 
ammonia  is  dissolved  in  the  other  four  ounces.  While  the 
albumen  is  briskly  stirred  with  a  glass  rod  the  bichromate 
solution  is  slowly  poured  in,  and  while  the  stirring  is  con- 
tinued the  ammonia  is  added  from  a  dropping  tube  until  the 
solution  turns  to  a  pale  straw  color.   The  solution  is  filtered 


76 


iiorgan's  half-tone 


slowly  through  a  tuft  of  filtering  cotton  into  a  clean  glass 
pouring-bottle,  when  it  is  ready  to  sensitize  the  zinc  plate. 

SENSITIZING  AND  PRINTING  THE  ZINC. 

After  the  zinc  plate  is  prepared  for  sensitizing  by  polish- 
ing with  charcoal  as  described,  it  should  not  be  allowed  to 
dry  before  sensitizing.  To  keep  it  any  length  of  time  before 
sensitizing,  it  must  be  put  in  a  tray  and  covered  with  clean 
water.  While  the  zinc  plate  is  still  wet  with  clean  water  it 
is  flowed  with  the  sensitized  albumen  in  the  same  manner  as 
collodion  is  flowed,  except  that  the  solution,  after  covering 
the  plate  and  driving  off  the  water  that  was  on  the  plate,  is 
allowed  to  run  to  waste.  The  zinc  is  coated  once  more  from 
the  diagonally  opposite  corner  and  the  solution  again  allowed 
to  waste.  This  coating  is  repeated  four  times.  The  last 
two  coatings  may  be  drained  from  the  plate  into  the  filter  to 
be  used  later.  The  plate  can  now  be  fastened  face  down  in  a 
whirler  and  dried  face  down  or  it  can  be  held  almost  vertical 
over  heat  so  that  surplus  solution  can  drain  off.  No  matter 
how  it  is  dried,  three  points  must  be  watched.  First,  that  no 
air  bubbles  are  allowed  to  rest  on  the  plate ;  secondly,  that  it 
is  dried  free  from  dust  particles;  and  lastly,  that  it  is  not 
heated  above  that  which  the  back  of  the  hand  can  withstand, 
as  overheating  will  coagulate  the  extremely  thin  film  of  albu- 
men. Of  course  the  sensitizing  and  drying  operations  are 
performed  in  a  room  lighted  only  by  a  yellow  light.  Though 
gaslight  or  an  incandescent  lamp  has  little  influence  on  the 
bichromatized  albumen  film,  still  it  is  better  to  use  only  yellow 
light. 

EXPOSING  TO  LIGHT  IN  THE  PRINTING-FRAME. 

When  the  sensitized  plate  is  cool  it  is  ready  for  exposure 
behind  the  negative.  Both  the  negative  and  plate  should  be 
the  same  temperature  to  avoid  sweating  when  in  contact. 
The  regulation  engravers'  printing-frame  is  used,  and  its 
thick  glass  is  cleaned  carefully.  No  particles  of  grit  should 
get  between  the  glasses,  or  one  or  both  of  them  may  be  broken 
under  the  great  pressure  required  to  produce  absolute  con- 
tact. A  backing  sheet  of  pure  gum  rubber  or  a  soft  and  thick 


RELIEF-LINE  ENGRAVING 


77 


felt  or  woolen  blanket  behind  the  metal  plate  will  give  the 
requisite  elasticity  and  prevent  much  glass  breakage. 

The  time  of  exposure  can  best  be  determined  by  experi- 
ment, for  the  strength  of  sunlight  varies  even  with  the  lati- 
tude, the  season  of  the  year  and  the  time  of  day.  So  also 
does  the  strength  of  the  electric  light  change  with  the  car- 
bons, current,  style  of  lamp  used,  and  distance  of  the  sensi- 
tive plate  from  the  arc.  A  few  trials  will  teach  the  proper 
exposure.  With  an  intense  negative  there  is  great  latitude  in 
exposure,  so  there  is  little  danger  of  overexposure  except  that 
it  may  thicken  the  lines. 

INKING  THE  EXPOSED  PRINT. 

There  are  so  many  makes  of  excellent  etching-ink  obtain- 
able everywhere  that  no  engraver  should  attempt  making  his 
own  etching-ink.  Ink  properly  covered  from  dust  and  air 
will  keep  for  centuries,  so  there  is  no  necessity  for  fresh  ink. 
Old  stiff  ink  needs  only  to  be  softened  with  a  little  linseed-oil 
varnish  or  a  vegetable  oil  to  be  made  ready  for  use. 

Should  a  regular  etching-ink  be  not  at  hand,  lithogra- 
phers' transfer-ink  will  be  found  to  answer  the  purpose,  and 
even  ordinary  printing-ink  will  work  providing  it  has  a  little 
Canada  balsam  incorporated  thoroughly  with  it. 

For  long  service  a  smooth  skin  lithographic  roller  is  best : 
a  composition  roller  lays  a  smoother  film  of  ink.  It  is  recom- 
mended to  spread  the  ink  on  the  warmed  plate  with  a  smooth 
skin  roller,  and  then  distribute  the  ink  in  intimate  contact 
with  the  albumen  film  with  a  composition  roller.  The  impor- 
tant thing  to  consider  for  the  best  work  is  to  get  a  thin  coat- 
ing of  stiff  ink  so  that  the  color  of  the  zinc  will  not  be  entirely 
hidden  and  that  the  plate  is  covered  perfectly.  This  can  only 
be  accomplished  by  continuous  rolling.  Should  too  much  ink 
be  on  the  plate  it  can  be  removed  by  cleaning  the  roller  and 
going  over  the  ink  with  the  clean  roller. 

DEVELOPING  THE  IMAGE. 

After  inking  the  warm  plate  in  a  yellow  light  it  is  laid  in 
a  tray  of  clean,  cold  water  without  allowing  any  air-bells  to 


78 


horgan's  half-tone 


adhere  to  its  surface.  The  tray  can  then  be  taken,  if  desired, 
into  daylight  to  develop  the  image.  The  image  should  show, 
if  the  coating  of  ink  is  thin  enough,  almost  immediately. 
A  good-sized  tuft  of  absorbent  cotton  is  wet  with  the  water 
and  gently  drawn  over  the  plate,  when  the  albumen  unacted 
upon  by  light  will  wash  away  from  the  plate,  carrying  with 
it  the  overlying  film  of  ink.  This  gentle  washing  with  the 
absorbent  cotton  is  continued  until  all  the  surplus  ink  is 
removed,  when  the  image  will  be  found  sharp  and  clean. 
A  good  rinsing  under  the  tap  will  free  the  plate  of  any  soluble 
albumen  and  loose  ink.  The  plate  is  then  dried  over  gentle 
heat  without  permitting  any  drops  of  water  to  rest  on  the 
image  while  drying.  Water  drops  are  usually  blown  from 
the  plate.  When  the  plate  is  dry  it  is  examined,  and  any 
broken  lines  or  dots  repaired  by  retouching  with  a  fine 
camel's-hair  brush  and  dilute  etching-ink.  It  is  then  ready 
for  powdering,  as  it  is  called. 

POWDERING  THE  PLATE. 

Much  of  the  smoothness  of  the  edge  of  the  lines  obtained 
by  etching  is  dependent  on  the  fineness  of  the  resinous  powder 
used  as  an  acid  resist,  so  that  too  much  attention  can  not  be 
paid  to  sifting  the  powder  through  a  silk  sieve  before  allow- 
ing it  to  attach  itself  to  the  ink  image  on  the  plate.  The  first 
resinous  or  "  topping "  powder  applied  is  usually  a  white 
powder  and  can  be  finely  ground  resin,  shellac,  dammar  or 
sandarac.  This  white  powder  is  kept  in  a  well-covered  box 
larger  than  the  largest  plate  used.  Some  of  the  white  powder 
is  shaken  all  over  the  surface  of  the  warmed  plate  and 
brushed  carefully  in  contact  with  the  ink  with  a  broad  and 
soft  camel's-hair  brush.  The  surplus  resin  is  removed  by 
brushing  with  a  large  wad  of  dry  absorbent  cotton  until, 
looking  over  the  surface  of  the  plate  held  level  toward  the 
light  and  even  with  the  eyes,  no  powder  is  seen  attached  to 
the  bare  metal. 

It  is  well  now  to  go  over  the  plate  with  finely  powdered 
dragon's-blood,  in  the  same  manner  as  the  white  powder  was 
used,  except  with  a  different  brush  and  tuft  of  cotton.  The 


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79 


dragon's-blood  powder  fills  in  between  the  fine  grains  of  the 
white  powder,  and  when  melted  makes  a  resinous  coating 
more  impervious  to  acid  than  if  the  white  powder  alone  was 
used. 

MELTING  THE  RESINOUS  POWDER. 

As  any  of  the  resinous  powders  used  melt  at  a  tempera- 
ture of  between  2500  and  3000  F.,  it  is  not  necessary  to  heat 
the  zinc  plate  beyond  3000  F.  Greater  heat  might  cause  the 
resin  to  melt  and  run  together  where  the  lines  are  extremely 
close  together  and  also  injure  the  zinc.  When  the  image  on 
the  metal  begins  to  appear  glossy  over  the  heat  it  is  suffi- 
ciently incorporated  with  the  ink,  and  the  plate  ( still  gripped 
with  the  broad-nosed  pliers  with  which  it  was  held  over  the 
heat)  is  coated  on  the  back,  edges  and  sides  with  a  thin 
asphalt  varnish  which  is  allowed  to  dry. 

ETCHING  THE  METAL  PLATE. 

The  etching  fluid  for  zinc  is  nitric  acid  diluted  with 
water.  For  the  first  "  bite,"  as  the  first  etching  is  called,  one 
ounce  of  400  Baume  nitric  acid  in  eighty  ounces  of  water  is 
sufficiently  strong.  This  etching  solution  is  put  in  a  rocking 
bath,  the  plate  placed  in  it,  and  the  solution  allowed  to  rock 
back  and  forth  over  the  plate  until  its  exposed  metal  surface 
is  covered  with  fine  bubbles  of  gas.  A  flat  camel's-hair 
brush  is  used  to  remove  these  gas  bubbles  while  the  bath  is 
kept  rocking.  The  constant  movement  of  the  etching  fluid 
over  the  surface  of  the  plate  prevents  the  further  formation 
of  gas  bubbles.  The  oxid  of  zinc  which  is  left  on  the  plate 
by  the  corrosion  of  the  etching  fluid  is  removed  at  intervals 
by  gentle  use  of  the  earner s-hair  brush.  The  plate  can  be 
turned  occasionally  so  that  the  etching  fluid  washes  over  it 
in  as  many  different  directions  as  possible. 

The  finest  lines  or  dots  on  the  plate  must  be  watched  to 
see  that  they  show  no  signs  of  reduction  in  width,  which 
would  indicate  that  the  etching  fluid  is  beginning  to  encroach 
on  the  sides  of  the  lines,  which  side  action  of  the  corrosive 
liquid  is  what  must  be  avoided  to  secure  proper  etching. 


80 


horgan's  half-tone 


When  tne  progress  of  the  etching  is  to  be  examined  the  zinc 
plate  must  be  taken  out  and  plunged  quickly  into  water  or 
held  under  the  tap  to  prevent  oxid  forming.  When  the 
exposed  surface  of  the  zinc  has  been  so  far  dissolved  away 
that  the  depth  can  be  felt  with  the  finger-nail  the  moisture 
may  be  removed  from  the  plate  with  a  dampened  chamois- 
skin  and  the  etching  examined  with  a  magnifying  glass. 
The  finest  lines  or  dots  in  the  image  are  the  ones  to  scrutinize. 
If  they  have  been  reduced  at  all  in  width  then  the  etching  has 
proceeded  too  far,  though  a  slight  reduction  is  made  up  for 
in  the  thickening  of  the  line  when  printed  from  later.  It  is 
astonishing  how  slight  the  depth  of  etching  need  be  to  retain 
etching  powder  in  the  next  operation. 

THE  SECOND  ETCHING. 

Before  proceeding  farther  with  the  etching  the  sides  of 
the  lines  must  be  protected  from  the  action  of  the  acid,  and 
this  is  clone  by  brushing  dragon's-blood  powder  against  the 
sides  of  the  lines  in  the  following  manner : 

Push  the  upper  edge  of  the  warmed  zinc  plate  through 
the  finely  sifted  dragon's-blood  powder  lying  on  the  bottom 
of  the  box  until  a  quantity  of  the  powder  is  scraped  up  on 
the  upper  part  of  the  plate.  Hold  the  plate  at  such  an  angle 
as  will  cause  the  powder  to  slide  on  the  surface  of  the  plate 
back  into  the  powder-box  from  the  lower  edge  of  the  plate, 
then  lay  the  plate  on  the  edge  of  the  box,  and  while  holding 
it  with  its  lower  edge  slightly  inclined  toward  the  bottom  of 
the  powder-box  brush  the  powder  into  the  box  with  a  wide 
and  soft  camel's-hair  brush,  keeping  in  mind  that  you  are 
brushing  the  powder  against  the  upper  sides  of  all  the  lines 
and  dots  on  the  plate.  Keep  up  this  brushing,  with  the  plate 
and  brush  at  the  same  angle,  the  latter  almost  vertical,  until 
all  of  the  powder  is  brushed  clean  from  the  exposed  zinc  that 
has  been  etched,  except  that  which  is  brushed  against  the 
upper  sides  of  the  lines  and  dots.  Without  jarring  the  plate, 
which  might  shake  down  the  powder  pressed  against  the  side 
of  the  lines,  grip  the  plate  with  the  wide-nosed  pliers  and 
hold  it  over  heat  until  the  dragon's-blood  is  melted  and 


RELIEF-LINE  ENGRAVING 


81 


attached  to  the  side  of  the  lines  and  dots.  Then  lay  the  zinc 
plate  on  a  cold  stone  or  iron  slab  to  cool.  Repeat  this  opera- 
tion by  brushing  the  dragon's-blood  powder  over  the  image 
in  the  three  other  directions  and  melting  the  powder  securely 
in  place  after  each  powdering  until  all  four  sides  of  the  dots 
on  the  plate  are  protected  with  dragon's-blood  powder. 

The  etching  bath  of  eighty  ounces  of  solution  may  be 
strengthened  with  the  addition  of  from  one  to  two  ounces  of 
nitric  acid  for  the  second  bite.  The  bath  is  rocked  as  before 
and  the  gas  bubbles  removed  when  they  form.  The  plate 
can  be  brushed  more  frequently,  and  the  etching  proceed 
until  the  plate  is  corroded  to  over  twice  the  depth  of  the  first 
bite,  when  it  is  taken  out,  washed  well  under  the  tap,  the 
moisture  dabbed  from  the  plate  with  the  damp  chamois-skin, 
and  the  plate  dried  and  examined. 

THE  THIRD  AND  FOURTH  ETCHINGS. 

The  warmed  plate  is  again  powdered  four  ways.  This 
time  the  powder  can  be  banked  in  considerable  quantity 
against  the  sides  of  the  lines  and  the  small  spaces  between 
the  lines  completely  filled  with  the  powder.  The  strength  of 
the  etching  solution  is  further  increased,  and  the  plate  can  be 
brushed  more  frequently  while  being  rocked  in  the  etching 
bath. 

Three  bites,  or  etchings,  is  usually  all  that  is  required  to 
get  sufficient  depth.  Should  a  fourth  etching  be  desired,  the 
operation  of  powdering  four  ways  is  repeated  once  more 
and  the  acid  bath  is  strengthened  still  further,  all  of  which 
can  be  learned  by  experience  and  good  judgment  better  than 
from  pages  of  description. 

Etching  machines  which  impel  the  etching  fluid  against 
the  plate  at  right  angles  to  its  surface  produce  far  more 
satisfactory  results  than  can  be  had  in  the  method  just 
described,  which  is  termed  "  tub  "  etching. 

CLEANING  THE  ACID  RESIST  FROM  THE  PLATE. 

No  better  means  of  removing  all  of  the  etching  resist 
from  the  zinc  plate  can  be  found  than  to  heat  the  plate  quite 
6 


82 


II0RGAN  S  HALF-TONE 


hot  and  pour  over  it  some  strong  lye  solution,  afterward 
scrubbing  back  and  front  with  a  strong  bristle  brush,  care 
being  taken  that  none  of  the  hot  lye  gets  on  the  skin  which  it 
will  remove  as  readily  as  it  does  the  acid  resist.  Strong 
caustic  potash  or  lye  has  a  corrosive  action  on  zinc,  therefore 
it  must  be  washed  off  quickly  under  the  tap  after  it  has  dis- 
solved away  the  acid  resist  from  the  plate.  The  water  is 
again  removed  from  the  cleaned  zinc  with  the  damp  chamois- 
skin.  The  plate  is  dried  quickly  to  prevent  oxidization,  and 
it  is  then  ready  for  proving ;  after  which  it  is  routed  with  a 
machine  for  that  purpose  and  turned  over  to  the  finisher  who 
engraves  out  any  defects,  raises  the  metal  where  parts  of  the 
image  have  been  etched  away  and  softens  the  lines  used  in 
shading  with  a  roulette  so  that  they  will  grade  off  to  white. 
The  finisher  works  with  the  copy  and  the  first  proof  before 
him,  and  the  perfection  of  the  finished  plate  depends  on  his 
training,  skill  and  judgment. 

ENAMEL  ACID  RESIST  ON  ZINC. 

One  reason  a  solution  containing  glue  called  "  enamel " 
is  not  used  more  commonly  on  zinc,  as  it  is  used  universally 
on  copper,  is  because  enamel  requires  to  be  carbonized  before 
it  will  become  an  acid  resist  and  zinc  will  melt  before  the  heat 
required  to  carbonize  is  reached. 

Enamel  is  used  on  zinc,  however,  by  observing  the  fol- 
lowing precautions :  First,  the  zinc  surface  is  given  a  slight 
grain  or  "  tooth " ;  chromic  acid  or  citrate  of  iron  and 
ammonia  is  used  in  the  sensitizer ;  a  hardening  bath  is  used 
to  make  the  glue  nonabsorbent  of  water ;  and  lastly,  an  alco- 
holic acid  solution  may  be  used  instead  of  an  aqueous  one  to 
etch  the  enamel-coated  plate  in.  By  keeping  these  precau- 
tions in  mind  enamel  can  be  used  on  zinc  by  the  following 
procedure : 

GRAINING  BATH  FOR  ZINC. 

The  grease  is  first  removed  from  the  sheet  of  polished 
zinc  by  laying  it  in  a  solution  of  caustic  potash  for  a  few 
minutes,  after  which  it  is  washed  well  under  the  tap  to 


RELIEF-LINE  ENGRAVING 


83 


remove  all  traces  of  the  potash  from  both  sides  of  the  zinc. 
It  is  then  laid  face  up  in  a  tray  containing  the  following- 


solution  : 

Water    30  ounces 

Powdered  alum   1  ounce 

Nitric  acid   Yi  ounce 


This  solution  is  allowed  to  flow  back  and  forth  over  the  sur- 
face of  the  zinc  while  it  is  brushed  evenly  with  a  broad 
bristle  brush.  After  a  few  minutes  the  surface  will  take  on 
an  even,  gray,  matt  surface,  when  it  is  washed  with  a  clean 
sponge  under  the  tap  to  remove  the  oxid  of  zinc. 

While  the  zinc  plate  is  still  wet  it  is  flowed  with  the  fol- 
lowing 

ENAMEL  SOLUTION  FOR  ZINC. 


Water    8  ounces 

Le  Page's  glue    4  ounces 

Ammonium  bichromate  160  grains 

Citrate  of  iron  and  ammonia   24  grains 


Dissolve  the  bichromate  in  4  ounces  of  the  water  and  add 
the  citrate.  Dissolve  the  glue  in  the  other  4  ounces  of  water 
and  pour  the  dissolved  salts  into  it  while  the  glue  solution  is 
being  stirred.  This  solution  will  not  keep  long,  though  it 
works  best  twelve  hours  after  being  made  up.  The  only 
precaution  to  use  with  it  is,  after  development,  to  remove  the 
water  from  the  enamel  by  flowing  the  plate  with  methylated 
alcohol  several  times.  Bake  the  enamel  to  a  light  brown. 

ENAMEL  FOR  ZINC  WITH  HARDENER. 

For  those  who  care  to  use  a  hardener  for  the  enamel  the 
following  formula  will  be  found  to  work  admirably : 


Water    10  ounces 

Le  Page's  glue   3  ounces 

Albumen,  white  of  a  fresh  egg   1  ounce 

Ammonium  bichromate   100  grains 

Chromic  acid    5  grains 


Le  Page's  glue  is  not  essential.  Any  good  quality  fish- 
glue  will  answer;  in  fact,  some  prefer  what  is  known  as 


84 


horgan's  half-tone 


belting  cement,  as  it  gives  a  still  tougher  enamel.  Care  must 
be  observed  with  unclarified  glues  to  filter  out  the  globules  of 
fat  that  may  be  seen  floating  on  the  surface. 

HARDENER  FOR  ENAMEL  ON  ZINC. 

The  hardener  used  with  the  above  enamel  is  made  as 
follows : 

Water    30  ounces 

Ammonium  bichromate    60  grains 

Chromic  acid    5  grains 

Methylated,  or  wood  alcohol   5  ounces 

The  developed  enamel-coated  plate  should  rest  in  this  harden- 
ing bath  for  from  three  to  five  minutes. 

The  secret  in  the  use  of  an  enamel  on  zinc  is  to  use  as 
strong  a  nitric  acid  bath  as  possible,  so  as  to  etch  the  plate 
quickly  and  wash  the  enamel  under  the  tap  only  when  abso- 
lutely necessary,  as  water  is  liable  to  soften  the  enamel. 


HALF-TONE  WITH  TWO-HUNDRED-LINE  SCREEN. 
Mr.  Frederick  E.  Ives. 
Suffolk  Engraving  Co.,  New  York  and  Boston. 


THE  HALF-TONE  PROCESS 


AS  APPLIED  TO 

RELIEF-PLATE  ENGRAVING  AND  USED  IN  EVERY  LARGE 
CITY  IN  THE  WORLD. 


The  term  "  Half-tone  "  is  a  misnomer  as  applied  to  the 
photomechanical  method  of  making  relief  blocks  for  the 
printing-press,  for  the  reason  that  the  word  "  half-tone  " 
refers  only  to  the  intermediate  color  between  the  extreme 
lights  and  the  strong  shades  of  a  picture,  while  the  half-tone 
process  of  engraving  reproduces  all  the  tones  of  a  picture 
including  the  high  lights  and  the  shadows.  The  term 
"  similigravure  "  in  French  expresses  the  idea  better,  but  the 
word  "  half-tone "  has  come  into  the  language  and  will 
remain. 

One  explanation  of  the  way  the  word  came  into  use  is 
that  in  the  early  days  of  the  process  it  was  usual  to  say  of  it 
that  it  "  reproduced  all  the  half-tones  of  the  photograph," 
and  this  was  eventually  shortened  to  the  "  half-tone  process," 
and  as  it  was  used  practically  first  in  the  United  States  the 
word  adopted  for  it  here  impressed  itself  on  other  languages 
until  now  "  der  Halbtoneprozess  "  is  applied  to  it  in  Ger- 
many and  "  Demi-teinte  proces  "  is  known  in  France. 

Half-tone  engraving  has  come  so  quietly  and  modestly 
into  use  that  no  one  realizes  how  extensive  is  the  place  in 
modern  civilization  it  occupies  nor  the  great  number  of  lines 
of  business  which  are  dependent  upon  it.  The  universally 
used  half-tone  block  is  responsible  for  great  changes  in  the 
manufacture  of  printing-presses,  paper  and  ink,  and  in  the 
greatly  increased  demand  for  these  products  has  built  up 
immense  manufacturing  industries  with  their  thousands  of 
workmen  making  fortunes  for  their  proprietors,  while  those 
who  brought  the  half-tone  block  to  its  present  state  of  perfec- 
tion have  been  satisfied  with  a  bare  living. 

Some  idea  of  the  importance  of  the  half-tone  block  in 
business  can  be  had  if  one  contemplates  what  would  happen 

85 


86 


morgan's  half-tone 


if  half-tone  engraving  should  stop  suddenly.  Think  of  the 
number  of  monthly  periodicals  and  weekly  publications  that 
would  collapse  immediately,  the  thousands  of  engravers, 
electrotypers,  printers,  pressmen,  inkmakers,  papermakers 
and  allied  tradesmen  that  would  be  out  of  employment  and 
the  millions  of  dollars  in  presses  that  would  go  into  the  scrap- 
heap.  Modern  business  is  so  dependent  on  advertising,  and 
extensive  advertising  is  made  attractive  chiefly  through  half- 
tone illustration,  that  it  will  be  understood  how,  through  the 
removal  of  half-tone  illustration,  business  would  lose  its 
stimulus.  Still  the  most  serious  blow  to  civilization,  through 
stopping  suddenly  the  making  of  half-tone  engraving,  would 
be  in  education,  for  illustrations  are,  after  all,  among  our 
chief  sources  of  information.  We  receive  mental  impres- 
sions from  them  quickest,  and  these  pictures  remain  longest 
in  our  memories,  while  they  are  at  present  and  long  will 
continue  to  be  the  only  universal  language. 

WHAT  IS  A  HALF-TONE? 

The  greatest  librarian  in  this  country  has  asked  the 
writer  "  How  can  I  distinguish  a  half-tone  from  a  lithograph 
or  a  photogravure.  They  all  appear  to  be  made  through  a 
screen."  By  "  half-tone  99  he  meant  an  impression  from  a 
half-tone  relief  block,  by  "  lithograph "  he  referred  to  a 
planograph  print  made  on  the  offset  press,  and  by  "  photo- 
gravure "  he  had  in  mind  a  rotary-photogravure.  A  study  of 
the  inserts  in  this  volume  with  a  magnifying  glass  will  help 
one  to  distinguish  the  different  processes  used.  The  rotary- 
photogravure  is  easily  distinguished  by  its  velvety  shadows 
devoid  of  screeny  effect,  while  in  the  lighter  tones,  where  the 
screen  is  visible,  it  separates  squares  of  the  same  area  but 
with  varying  quantities  of  ink  in  the  squares.  An  offset 
print  is  usually  on  a  rough-surfaced  paper,  the  half-tone  dots 
having  a  soft  appearance,  while  the  relief  half-tone  impres- 
sion is  generally  on  a  coated  stock  with  white  dots  like  needle- 
points in  the  extreme  shadows  and  a  gradation  into  the  most 
delicate  black  dots  in  the  high  lights.  Still  an  expert  will  be 
deceived  at  times  as  to  the  method  used  in  producing  an 


DARGAVEL  WAVY-LINE  SCREEN. 
John  Swain  &  Son,  Ltd.,  London. 


THE  HALF-TONE  PROCESS 


87 


illustration,  owing  to  the  applications  of  the  half-tone  screen 
becoming  so  varied  and  the  printing  methods  so  numerous. 

THE  HALF-TONE  SCREEN. 

The  early  experimenters  seeking  a  method  for  trans- 
lating the  tones  of  a  photograph  into  lines  and  dots,  in  some 
approach  to  the  results  of  the  wood  engraver,  dreamed  that 
it  might  possibly  be  done  through  a  grating  or  screen  of  some 
kind,  and  numerous  were  the  kinds  of  screens  or  gratings 
used.  The  writer  reasoned  out  that  the  grating  should  be 
one  consisting  of  apertures,  and  so  the  first  half-tones  he 
made  between  1877  and  1880  were  made  through  perforated 
cardboard. 

The  half-tone  screen  used  in  the  making  of  relief  blocks 
to-day  is  simply  an  opaque  plane  surface  through  which 
square  apertures  are  pierced.  These  apertures  are  uniform 
in  size,  mathematically  equidistant,  and  in  area  are  one-third 
the  area  of  the  opaque  plane  surface.  We  owe  the  present 
half-tone  screen  to  Mr.  Frederick  E.  Ives,  who  in  the  winter 
of  1885-6  sealed  two  single-line  screens  together,  and  to 
Mr.  Max  Levy,  who  in  1893  perfected  the  manufacture. 

THEORIES  AS  TO  HALF-TONE  DOT  FORMATION. 

An  explanation  of  the  action  of  the  rays  of  light  reflected 
from  the  object  through  the  diaphragm  in  the  lens  and  then 
through  the  apertures  in  the  screen  to  form  dots  of  different 
shapes  and  areas  on  the  sensitive  photographic  plate  would 
require  extremely  complicated  diagrams  and  such  a  mixture 
of  words  and  phrases  as :  "  Dioptric  image,"  "  penumbral 
effect,"  "  luminiferous  ether,"  "  irradiation,"  "  diffraction," 
"  interference  fringes,"  "  halation,"  "  fluorescence,"  and  the 
"  undulatory  "  and  "  vibratory  "  theory  of  light.  All  of 
which  will  be  spared  the  reader  as  being  beyond  the  purpose 
of  this  book.  We  will  consider  only  the  practical  methods 
employed  in  making  a  half-tone  block. 

Half-tone  negative-making  is  one  of  the  most  intricate 
lines  of  work  in  which  a  photographer  can  be  employed.  It 


88 


horgan's  half-tone 


requires  a  natural  taste,  or  a  cultivated  judgment,  as  to  tone 
values,  a  knowledge  of  ordinary  negative-making  and  a  skill 
in  the  use  of  diaphragms  and  the  manipulation  of  screen 
distances  that  can  best  be  acquired  by  actual  practice. 

Added  to  this  must  be  apparatus  as  nearly  perfect  as  can 
be  found  so  readily  in  the  market  to-day.  There  are  at  least 
five  excellent  makes  of  lenses,  any  of  them  rather  expensive 
it  would  seem,  but  really  sources  of  much  economy  from  the 
speed  at  which  they  work  coupled  with  their  superior  defini- 
tion. A  good  camera  is  a  most  necessary  piece  of  apparatus. 
One  in  which  the  screen  support  is  part  of  the  camera-box 
and  not  in  the  plateholder  is  to  be  preferred,  for  it  is  not 
only  risky  to  carry  a  valuable  screen  in  the  plateholder  from 
darkroom  to  camera,  but  it  is  a  waste  of  energy  as  well.  The 
camera-box,  the  slides  on  which  it  moves,  and  the  copy-board 
holder  must  be  so  rigid  that  perfect  parallelism  is  maintained 
at  all  times  between  copy-board,  half-tone  screen  and  sensi- 
tive plate.  The  mechanism  for  regulating  the  distance 
between  the  half-tone  screen  and  the  sensitive  plate,  while 
maintaining  perfect  parallelism  between  them,  should  have 
a  micrometric  adjustment.  Should  a  prism  be  used  with  the 
camera,  then  it  must  be  kept  at  absolute  right  angles  with 
the  copy-board.  The  plateholder  should  be  always  in  perfect 
condition  and  the  camera-stand  arranged  to  absorb  all  vibra- 
tion. It  is  needless  to  add  that  the  half-tone  screens  must  be 
perfect. 

THE  SCREENY  EFFECT  IN  HALF-TONES. 

While  on  the  subject  of  the  half-tone  screen  some  ques- 
tions frequently  asked  might  be  answered.  In  the  first  place, 
the  invariable  alignment  of  the  dots  at  angles  of  forty-five 
degrees  to  the  sides  of  the  screen  is  selected  because  it  was 
found  at  that  angle  they  were  least  objectionable.  Were 
they  arranged,  for  instance,  horizontally  and  vertically,  they 
would  be  most  obvious.  Would  not  a  grain  screen  be  more 
pleasing?  Grain  screens  are  in  use.  A  most  excellent 
exhibit  of  engraving  through  such  a  screen  is  shown  in  this 
book.    It  has  been  found  in  practice  that  grain  screens  do 


FIRST  PHOTOENGRAVING. 
Portrait  of  Cardinal  d'Ambrose,  by  Joseph  Nicephore  Niepce. 
Reproduction  by  Barnes-Crosby  Company,  Chicago,  from  a  copy  in  the  possession 
of  Mr.  Albert  H.  Walker,  New  York. 


THE  HALF-TONE  PROCESS 


89 


not  give  in  the  highest  lights  and  deepest  shadows  the  deli- 
cate definitions  or  gradations  of  the  cross-line  screen.  Can 
not  screens  be  made  with  a  less  mechanical  pattern  than  cross 
bars?  As  the  mechanical  pattern  of  the  screen  is  governed 
largely  by  the  shape  of  the  aperture  in  the  diaphragm,  with 
the  ordinary  half-tone  screen  the  pattern  can  be  varied  at 
will  and  has  been  so  changed,  but  there  is  no  great  demand 
for  the  change. 

Gen.  Frederick  W.  Von  Egloffstein's  half-tone  screens 
used  in  New  York  in  1868  were  made  with  a  wavy  line,  and 
the  results  were  not  so  objectionable  as  the  straight  lines. 
Mr.  A.  Dargarvel,  of  London,  has  in  use  a  waved-line  screen. 
A  pleasing  example  of  work  engraved  with  it  is  shown  else- 
where. 

LIGHTS  FOR  MAKING  HALF-TONES. 

The  half-tone  screen  with  its  transparent  openings  but 
one-third  of  the  opaque  area  offers  so  much  obstruction  to 
the  light  in  negative-making  that  a  strong  flood  of  light  is 
desirable  to  illuminate  the  copy.  In  cases  where  the  subject 
is  to  be  enlarged,  sunlight,  if  available,  is  to  be  preferred. 
When  the  copy  is  large  and  in  colors,  such  as  a  painting, 
drawing,  decoration,  rug,  carpet,  wall-paper,  or  a  large  sur- 
face of  any  kind  requiring  even  illumination,  then  there  is 
no  light  to  compare  with  daylight  reflected  from  a  northern 
sky.  So  also  when  making  the  half-tone  negative  direct 
from  natural  objects.  But  when  the  copy  is  largely  the  repro- 
duction of  photographs,  wash  drawings  and  plane  surfaces 
of  small  dimension,  then  electric-light  illumination  is  pre- 
ferred, chiefly  on  account  of  its  steadiness.  In  fact  no  half- 
tone plant,  no  matter  how  extensive  its  provision  for  day 
lighting,  should  be  without  electric  lamps  as  a  substitute  or 
accessory  when  daylight  fails. 

For  newspapers,  where  negatives  must  be  made  at  night, 
electric  illumination  is  of  course  depended  on,  and  it  makes 
little  difference  whether  the  engraving  plant  is  located  in 
cellar  or  garret,  providing  the  ventilation  and  temperature  is 
right. 


90 


horgan's  half-tone 


Just  here  we  will  consider  the  half-tone  collodion.  It 
should  possess  certain  special  properties.  It  must  be  quick- 
working.  It  should  give  detail  in  the  shadows  and  still 
supply  strong  contrasts.  A  collodion  containing  all  these 
properties  would  be  ideal,  though  it  is  thus  far  impossible  of 
attainment  for  several  reasons:  The  quicker  a  collodion 
works,  the  less  contrasty  it  is;  while  a  contrasty  collodion 
means  one  that  will  not  give  detail  in  the  shadows,  so  that 
an  adequate  half-tone  collodion  must  be  one  of  compromises. 

In  compounding  a  half-tone  collodion  it  should  be  remem- 
bered that  iodids  give  contrast  while  the  bromids  decrease 
contrast,  at  the  same  time  giving  greater  detail  in  the  shad- 
ows. The  ammonium  salts  supply  a  collodion  that  can  be 
used  soon  after  making,  but  will  not  keep.  A  collodion  made 
with  the  cadmium  salts  will  require  weeks  to  "  ripen,"  as  it  is 
called  when  a  collodion  is  in  the  best  condition  to  use,  and  a 
cadmium  collodion  will  keep  in  a  workable  condition  for 
months.  The  quality  of  the  guncotton  (pyroxylin)  used  has 
considerable  influence  on  the  density  and  coarseness  of  grain 
of  the  negative,  so  that  care  must  be  taken  in  its  selection, 
though  even  the  best  brand  will  vary  in  quality  at  different 
times. 

HALF-TONE  COLLODION  FORMULA. 

The  first  thing  necessary  is  that  the  ingredients  in  a  half- 
tone collodion  be  pure.  Once  a  reliable  maker  of  chemicals 
is  found  he  should  be  patronized,  and  not  forsaken  for  the 
first  one  that  offers  a  cheaper  article  "  just  as  good."  The 
alcohol  must  be  guaranteed  to  be  a  ninety-five-per-cent  grain 
alcohol,  the  ether  should  be  sulphuric,  U.  S.  P.,  with  a  specific 
gravity  of  about  .725.  The  ammonium  iodid  must  be  U.  S.  P. 
in  crystals  about  the  color  of  light-brown  sugar,  for  the 
reason  that  collodion  made  with  it  ripens  quicker  —  that  is, 
it  can  be  used  a  day  or  so  after  being  mixed.  The  white 
iodid  of  ammonium  can  be  used,  though  it  is  generally  neces- 
sary to  add  a  few  drops  of  tincture  of  iodin  to  the  collodion 
to  ripen  it.  The  cadmium  bromid  should  be  in  white  crystals. 


PHOTOENGRAVING  OF  i860,  PRETSCH  PROCESS. 
Reproduction  by  Ransom  Engraving  Co.,  Ltd.,  Winnipeg,  Canada. 


THE  HALF-TONE  PROCESS  91 

The  proportion  of  a  simple  and  most  satisfactory  half- 
tone collodion  is  the  following : 

Ether,  sulphuric,  U.  S.  P.,  725   10  ounces 

Alcohol,  95  per  cent,  grain   10  ounces 

Guncotton  (pyroxylin)   180  grains 

Ammonium  iodid,  brown  100  grains 

Cadmium  iodid    40  grains 


The  better  way  to  use  the  formula  is  to  remember  that 
for  every  ounce  of  the  mixture  of  ether  and  alcohol  6  grains 
of  cotton  is  used  with  5  grains  of  ammonium  iodid  and  2 
grains  of  cadmium  bromid. 

Some  operators  use  a  little  chlorid  of  calcium  in  the 
collodion.  The  writer  can  not  see  any  advantage  in  its  intro- 
duction, while  it  adds  to  the  complication  when  purifying  the 
silver  bath.  A  45-grain-to-the-ounce  silver  bath  is  recom- 
mended with  this  collodion. 

The  preparation  and  care  of  the  silver  bath,  with  instruc- 
tions for  its  purification  when  contaminated  with  foreign 
matter,  is  described  in  the  chapter  on  Photolithography. 

GETTING  IT  IN  THE  NEGATIVE. 

In  the  early  days  of  half-tone  negative-making,  before 
staging,  reetching  and  the  skill  of  the  finisher  in  bringing 
the  flat-etched  half-tone  to  reproduce  the  copy  came  into  use, 
it  was  necessary  for  the  half-tone  photographer  to  get  all 
the  gradations  in  the  negative.  He  had  no  tables  of  screen 
distances  and  diaphragm  apertures  or  automatic  appliances 
to  assist  him.  He  did  work  so  well  that  it  is  a  source  of 
wonderment  to  present-day  processworkers  when  they  run 
across  half-tones  in  the  magazines  and  publications  of  1892- 
93.  He  reached  correct  screen  distance  and  the  proper  dia- 
phragms by  observation  of  the  effects  of  the  screen  upon  the 
ground  glass,  and  this  the  beginner  at  half-tone  negative- 
making  is  recommended  to  do. 

AS  TO  THE  DIAPHRAGMS. 

The  half-tone  photographer  should  have  had  previous 
training  in  line  negative-making  and  have  learned  the  proper 


92 


horgan's  half-tone 


use  of  diaphragms  and  the  correct  periods  of  time  for  expo- 
sure to  get  sharp  and  perfect  negatives  of  any  subject  copied. 

The  principles  of  half-tone  negative-making  are  similar 
to  line  negative-making  as  far  as  getting  a  negative  of  the 
copy  sharp  to  the  corners  —  one  difference  being  that  the 
interference  of  the  screen  increases  the  exposure  at  least  four 
times  what  it  would  be  without  the  screen.  There  is  a  com- 
mon mistake  that  the  screen  sharpens  the  image  upon  the 
ground  glass.  It  is  the  diaphragm  in  the  lens  that  produces 
the  sharpness  of  image.  If  the  diaphragm  used  in  the  lens 
when  making  a  half-tone  negative  will  not  produce  a  crisp 
image  without  the  screen,  then  the  introduction  of  the  screen 
will  lessen  rather  than  improve  the  definition. 

CHOOSING  THE  NORMAL  DIAPHRAGM. 

Hence,  the  first  thing  to  consider  in  the  choice  of  a 
diaphragm  for  half-tone  negative-making  is  whether  it  will 
cut  the  image  sharp  to  the  corners  of  the  plate.  For  the 
beginner  it  is  recommended  that  he  use  three  round  dia- 
phragms, the  iris  diaphragms  in  the  lens  being  suitable.  Let 
the  copy  chosen  to  experiment  with  be  a  photograph  neither 
too  flat  nor  too  contrasty,  but  with  the  proper  gradations  of 
light  and  shade. 

The  required  size  of  the  half-tone  and  the  focus  of  the 
image  can  be  had  on  the  ground  glass  without  a  diaphragm 
and  without  the  half-tone  screen,  if  the  camera  is  one  in 
which  the  screen  can  be  swung  out  of  the  way  or  is  carried 
in  the  plateholder.  Should  the  screen  be  in  front  of  the 
ground  glass  it  must  be  separated  from  the  ground  glass  as 
far  as  possible  until  the  proper  size  and  focus  of  the  image 
are  obtained. 

TO  FIND  THE  SCREEN  DISTANCE. 

When  the  largest  round  diaphragm  that  can  be  used 
and  obtain  a  sharp  image  is  selected  insert  it  in  the  lens. 
Then  move  the  screen  close  to  the  ground  glass  by  the 
mechanism  for  that  purpose.  The  cross-bars  on  the  screen 
will  be  found  to  throw  sharp  shadows  on  the  ground  glass 


HALF-TONE  OF  1868. 
By  General  Frederick  W.  Von  Egloffstein. 
Reproduction  by  F.  A.  Ringler  Company,  New  York. 


THE  HALF-TONE  PROCESS 


93 


with  square  spots  of  light.  Now  while  slowly  moving 
the  screen  away  from  the  ground  glass  study,  with  a 
focusing  glass  or  magnifying  eyepiece,  the  screen  effects 
in  the  high  lights  of  the  copy.  When  a  "  chess-board " 
formation  of  light  squares  and  opaque  squares  is  seen, 
just  touching  each  other  at  diagonal  corners,  then  fix  the 
screen  at  that  distance  from  the  ground  glass,  for  this  is 
the  effect  desired  in  the  middle  tones  of  the  finished  print, 
and  the  diaphragm  with  which  it  is  formed  is  called  the 
"  normal  stop." 

THE  HIGH-LIGHT  STOP. 

The  largest  of  the  three  diaphragms  used  is  called  the 
"  closing-up  99  or  "  high-light  stop."  This  is  selected  by  leav- 
ing the  screen  at  the  distance  chosen,  through  the  use  of  the 
normal  stop,  and  by  using  larger  diaphragms  watch  the 
effect  on  the  ground  glass.  It  will  be  noticed  that  as  the 
aperture  in  the  diaphragm  increases  in  size  the  screen  shad- 
ows on  the  ground  glass  become  less  obvious  until  they 
disappear  altogether.  When  the  screen  shadows  become 
merely  black  dots  on  the  ground  glass  then  the  aperture  in 
the  diaphragm  is  correct  for  the  high-light  exposure  and 
this  diaphragm  will  be  termed  the  high-light  stop. 

SELECTING  THE  SHADOW  STOP. 

The  diaphragm  used  to  give  the  small  white  dots  in  the 
shadows  of  the  finished  proof  is  called  the  "  shadow  stop." 
This  can  be  one-half  or  less  the  diameter  of  the  normal  stop. 
The  effect  of  this  stop  will  be  understood  by  inserting  it  in 
the  lens  and  covering  the  copy  with  a  sheet  of  white  paper ; 
then  observe  the  small  dots  of  light  formed  on  the  ground 
glass.  As  the  aperture  of  this  diaphragm  is  enlarged  the 
light  dots  increase  in  size  on  the  ground  glass,  and  two  points 
must  be  remembered  in  selecting  this  shadow  stop :  that  the 
smaller  it  is,  the  longer  the  exposure  required  and  the  less 
"  cutting  "  will  be  necessary  on  the  negative  film  later  to 
reduce  the  dots  in  size ;  while  if  a  larger  shadow  stop  is  used 
and  the  dots  develop  too  large,  they  can  be  reduced  by  the 
cutting  solution. 


94 


horgan's  half-tone 


Now  that  the  screen  distance  and  diaphragms  are  selected 
by  observation  the  correct  exposure  for  each  diaphragm  must 
be  determined,  and  that  can  be  done  by  experiment.  Here  is 
a  plan  for  obtaining  at  one  trial  most  information  regarding 
the  proper  periods  of  exposure.  It  is  done  by  making  three 
exposures  on  a  single  sensitive  plate,  the  subject  being  a 
wash-drawing  or  a  good  photograph. 

Let  us  suppose  the  copy  is  strongly  illuminated  and  the 
reduction  is  one-half,  the  normal  diaphragm  required  to  make 
the  copy  sharp  to  the  corners  is  34  incn  in  diameter,  the 
high-light  stop  is  inch,  and  the  shadow  stop  is  y%  inch. 
We  will  make  out  a  tentative  table  of  trial  exposures  like 
this: 

A.  Shadow  stop  .  .y$  inch  diameter.  .Exposure   4  minutes 

B.  Normal  stop  inch  diameter.  .Exposure   2  minutes 

C.  High-light  stop.J^  inch  diameter.  .Exposure  y2  minute 

THREE  TRIAL  EXPOSURES. 

The  three  exposures  on  the  same  negative  are  made  in 
this  way :  After  placing  the  plateholder  containing  the  sensi- 
tive plate  in  the  camera,  draw  the  slide  so  as  to  uncover  for 
exposure  one-third  of  the  sensitive  plate;  this  we  will  call 
exposure  A.  Then  by  drawing  the  slide  again  expose  two- 
thirds  of  the  plate  for  exposure  B,  and  finally  expose  the  full 
plate  for  exposure  C. 

Before  making  exposure  A,  the  shadow  stop  has  been 
inserted  in  the  lens ;  then  remove  the  cap  from  the  lens  for 
four  minutes.  For  exposure  B  the  normal  stop  is  inserted  in 
the  lens  and  the  cap  is  withdrawn  for  two  minutes.  For 
exposure  C  the  high-light  stop  is  inserted  in  the  lens  and  the 
latter  uncapped  for  one-half  minute. 

Development  of  this  plate  will  exhibit  on  section  C  the 
effect  of  the  high-light  stop  alone;  section  B  will  show  the 
effect  of  the  high-light  stop  and  the  normal  stop;  and  section 
A  will  demonstrate  the  result  of  the  exposures  of  all  three 
stops.  To  study  properly  the  effect  of  these  trial  exposures 
the  negative,  after  fixing  in  cyanid  of  potassium,  should  first 


A  HIGH-LIGHT  HALF-TONE  OF  1880. 
By  S.  H.  Horgan. 


THE  HALF-TONE  PROCESS 


95 


be  intensified  with  copper  and  silver  as  explained  in  the 
chapter  on  line  negative-making. 

After  intensification,  if  the  shadow  dots  are  not  intense 
enough  in  section  A,  the  checker-board  pattern  not  strong 
enough  in  the  middle  tones  of  section  B,  or  even  in  section  A, 
and  should  the  high  lights  not  show  a  tendency  to  close  up 
in  section  C  and  be  almost  entirely  closed  in  section  A,  then 
the  exposures  on  all  three  stops  have  not  been  long  enough. 
Should  one  or  two  of  the  exposures  be  sufficient,  this  trial 
negative  will  show  it.  If  on  the  other  hand  the  exposures 
seem  to  have  been  carried  too  far,  then  try  the  effect  of 
cutting  the  negative  as  will  be  explained  later. 

KEEP  A  RECORD  OF  EXPOSURES. 

Just  here  the  reader  is  recommended  to  keep  a  record  of 
each  negative  with  all  the  factors  that  entered  into  the 
making  of  it.  There  are  exposure  books  for  dry-plate  pho- 
tographers' use  that  can  be  made  to  answer  the  purpose 
admirably.  First  the  negative  is  numbered,  then  is  recorded 
the  title  and  kind  of  copy,  the  strength  and  kind  of  light  and 
its  distance  from  the  copy,  the  reduction  or  enlargement, 
screen  pitch,  distance  from  the  sensitive  plate,  number  and 
kinds  of  diaphragms  used  and  the  various  periods  of  expo- 
sure, together  with  the  features  of  the  intensification  and  the 
reduction  or  "  cutting  "  of  the  negative.  When  it  is  possible 
to  secure  proofs  of  the  engravings  before  finishing,  they  can 
be  kept  in  a  scrap-book  numbered,  as  are  the  negatives,  so 
that  at  any  time  there  is  a  "  make-over  "  the  method  employed 
in  making  the  first  negative  may  be  consulted  and  suggestions 
for  improvement  studied  out.  In  this  way  one  has  always 
before  him  "  past  performances,"  for  experience  is,  after  all, 
the  best  teacher. 

SCREEN  DISTANCE  AND  EXPOSURE  AT  ONE  TRIAL. 

Another  way  suggested  to  secure  several  trial  exposures 
on  a  single  plate  is  this:  The  same  procedure  may  be 
observed  as  described  for  the  previous  trial  negative,  as  far 


96 


horgan's  half-tone 


as  use  of  the  diaphragms  and  the  three  different  exposures, 
except  that  when  putting  the  sensitive  plate  in  the  holder,  if 
it  is  one  that  also  carries  the  half-tone  screen,  rest  the  lower 
edge  of  the  sensitized  plate  in  its  proper  place  but  allow  the 
upper  edge  of  the  plate  to  rest  against  the  half-tone  screen, 
the  latter  being  pushed  away  from  the  sensitized  plate  as  far 
as  possible.  If  the  sensitive  plate  is  a  wet  plate  it  is  neces- 
sary to  have  a  strip  of  blotter  between  the  upper  edge  of  the 
plate  and  the  screen  to  keep  them  from  touching.  The  wet 
plate  has  of  course  been  properly  drained  and  its  upper  edge 
wiped  dry  before  putting  in  the  holder.  This  will  give  a 
wedge-shaped  screen  distance,  beginning  with  less  than  one- 
sixteenth  of  an  inch  at  the  top  of  the  negative,  and,  say,  six- 
sixteenths  of  an  inch  at  the  bottom.  On  developing  this 
plate  and  fixing  in  cyanid  of  potassium  there  will  be  found  a 
line  somewhere  between  the  top  and  bottom  where  the  screen 
distance  is  correct.  To  find  this  proper  distance  it  will  be 
necessary  only  to  indicate  the  line  of  correct  distance,  put  the 
negative  back  in  its  original  position  in  the  plateholder  and 
measure  the  space  between  the  correct  line  of  distance  and 
the  half-tone  screen  to  find  the  correct  screen  distance. 

REDUCING,  OR  "  CUTTING/'  THE  NEGATIVE. 

The  semiopaque  fringe  seen  with  a  magnifying  glass 
around  the  edge  of  the  dots  in  the  half-tone  negative,  after 
intensification,  must  be  dissolved  away  so  as  to  leave  each  dot 
sharp  and  equally  intense  over  its  whole  area.  This  operation 
is  called  "  cutting,"  and  the  cutting  solution  can  be  made 
from  two  stock  solutions  as  follows : 


A.  Water    10  ounces 

Potassium  iodid    I  ounce 

Iodin,  crystals    V2  ounce 

B.  Water    10  ounces 

Potassium  cyanid   V2  ounce 


For  use,  take  y2  ounce  of  the  iodin  solution  A  in  10 
ounces  of  water  and  add  some  of  the  cyanid  solution  B 
slowly  to  the  wine-colored  iodin  solution  until  it  becomes  just 
transparent,  and  you  have  the  "  cutting  solution." 


A  COMBINATION  PLATE. 
Folsom  &  Sunergren  Co.,  Boston. 


THE  HALF-TONE  PROCESS 


97 


Flow  this  cutting  solution  over  the  whole  negative  image 
in  one  sweep,  as  is  done  with  developer;  allow  it  to  flow 
back  and  forth  over  the  negative  a  few  times ;  drain  it  back 
into  its  bottle,  and  watch  the  effect  on  the  fringe  on  the  high- 
light apertures  in  the  negative  and  the  shadow  dots,  the 
latter  particularly. 

It  is  advisable  to  do  this  work  over  a  sink  with  a  tap  of 
water  within  easy  reach  so  that,  if  necessary,  a  stream  of 
water  may  be  turned  on  instantly  over  the  half-tone  image 
to  stop  the  action  of  this  reducing  solution.  Should  the 
solution  act  too  quickly  it  must  be  diluted  with  water,  for  it 
is  necessary  that  it  dissolve  away  the  fringe  from  around  the 
dots  very  slowly. 

Of  course  local  reduction  can  be  had  by  pouring  the  solu- 
tion on  the  part  to  be  reduced,  allowing  it  to  flow  back  into 
its  bottle,  and  then  rinsing  the  negative  at  once  with  water. 
Repeat  these  operations  until  the  local  reduction  is  had. 

After  the  negative  image  is  reduced  or  "  cut "  sufficiently 
it  is  blackened  by  flowing  over  it 

Water    10  ounces 

Sodium  sulphid   I  ounce 

Should  the  half-tone  negative  not  have  density  enough 
it  can  be  treated  once  more  with  the  copper  and  silver  inten- 
sifier,  followed  with  the  cutting  solution  and  sodium  sulphid, 
taking  care  to  wash  the  negative  well  between  each  treat- 
ment. 

ANOTHER  NEGATIVE  REDUCTION  METHOD. 

By  using  the  A  and  B  components  of  the  cutting  solution 
heretofore  mentioned  separately,  the  reduction  of  the  dots 
may  be  brought  about  in  a  more  satisfactory  manner  for  the 
reason  that  the  operation  can  be  more  easily  watched. 

After  fixing  the  negative  in  cyanid  and  intensification 
with  copper  and  silver  as  described,  take  one  ounce  of  the 
A  solution  in  ten  ounces  of  water  and  flow  the  half-tone 
negative  with  it.  The  film  will  gradually  become  a  beautiful 
cream  color.  When  this  color  has  penetrated  through  to  the 
back  of  the  film,  as  seen  through  the  glass  support,  the  nega- 

7 


98 


h organ's  half-tone 


tive  may  be  rinsed  under  the  tap  and  flowed  with  the  cyanid 
of  potassium  solution  B  diluted  also  ten  times  with  water. 
As  the  transparent  half-tone  dots  in  the  negative  will,  by 
reflected  light,  appear  black  against  a  light  cream  ground, 
the  action  of  the  cutting  solution  can  be  studied  readily  and 
stopped,  when  it  has  proceeded  far  enough,  by  washing  the 
negative  well  under  the  tap ;  after  which  the  negative  film  is 
blackened  with  the  sodium  sulphid  solution  before  mentioned. 

HALF-TONE  NEGATIVE  PRINCIPLES. 

We  have  been  considering  the  making  of  a  half-tone 
negative  from  perfect  copy.  As  the  greater  portion  of  the 
copy  supplied  for  reproduction  in  half-tone  is  anything  but 
normal  copy,  being  either  too  flat  or  too  contrasty,  too  light 
or  too  dark,  a  few  of  the  principles  governing  the  treatment 
of  abnormal  copy  will  be  stated  here. 

To  obtain  a  contrasty  half-tone  from  flat  copy,  increase 
the  screen  distance  or  enlarge  the  high-light  stop.  Be  care- 
ful not  to  overtime  the  negative,  but  carry  the  development 
as  far  as  possible  and  intensify  several  times  if  necessary. 

From  overcontrasty  copy  a  negative  with  less  contrast 
may  be  had  by  reducing  the  screen  distance  or  the  size  of  the 
high-light  stop ;  overexpose,  but  be  careful  not  to  over- 
develop. After  intensification,  local  cutting  of  the  high  lights 
will  reduce  the  contrast  still  further  if  found  necessary. 

For  light  copy  overexposure  must  be  avoided,  while  with 
dark  copy  plenty  of  time  should  be  allowed  in  the  exposure. 

Red-toned  photographs  on  glossy  printing-out  paper 
make  the  best  copy  but  require  long  exposure. 

Glossy  black  prints  of  the  Velox  order  make  the  next 
best  copy,  though  they  also  require  long  exposure. 

FLASHING  SHOULD  BE  AVOIDED. 

Flashing  is  a  practice  resorted  to  in  the  case  of  copy  with 
extremely  dark  shadows  that  would  not  reflect  much  light. 
It  is  done  by  covering  up  the  copy  with  a  sheet  of  white 
paper  and  exposing  the  sensitive  plate  to  it  while  a  very  small 
diaphragm  is  inserted  in  the  lens.  The  exposure  is  for  about 


THE  HALF-TONE  PROCESS 


99 


one-twenty-fifth  the  total  exposure  with  the  other  dia- 
phragms. This  gives  a  small  dot  in  the  deep  shadows,  pro- 
duced artificially,  and  the  practice  is  to  be  discouraged  except 
in  the  case  of  newspaper  half-tones  when  the  small  dots  in 
the  shadows  of  the  plate  assist  in  the  stereotyping  and 
printing. 

Gray  matt  bromid  or  platinotype  prints  require  less  expo- 
sure, and  are  most  frequently  to  be  treated  as  flat  copy. 

POINTS  IN  HALF-TONE  NEGATIVE-MAKING. 

Exposure  is  the  most  important  factor  of  all  in  making 
half-tone  negatives.  Underexposure  can  rarely  be  corrected 
by  intensification.  Overexposure  can  most  often  be  over- 
come by  use  of  the  cutting  solution. 

As  the  camera  bellows  is  extended  the  screen  distance 
should  increase.  Long-focus  lenses  require  much  screen 
distance. 

Short-focus  lenses  require  short-screen  distance,  for  the 
nearer  the  lens  is  to  the  sensitive  plate  the  shorter  must  be 
the  screen  distance. 

A  fixed  screen  distance  can  be  kept  with  each  screen  used 
for  all  reductions  and  enlargements,  the  only  change  being 
made  in  the  size  of  the  stops,  these  being  increased  in  size 
with  enlargements  and  reduced  with  reductions. 

The  coarser  the  screen  used,  the  larger  the  diaphragms ; 
the  finer  the  screen,  the  smaller  the  diaphragms. 

The  screen  opening  is  in  the  same  proportion  to  the 
screen  distance  as  the  aperture  in  the  diaphragm  is  to  the 
distance  between  the  diaphragm  and  the  sensitive  plate,  so 
that  having  any  three  of  the  factors  it  is  easy  to  calculate 
the  fourth. 

The  farther  away  the  screen  can  be  kept  from  the  sensi- 
tive plate  and  the  smaller  the  normal  stop  used,  the  more 
detail  will  be  retained  in  the  half-tone  reproduction. 

The  closer  the  screen  to  the  sensitive  plate,  the  more 
"screeny"  the  result;  while  if  the  screen  is  removed  too 
far  from  the  sensitive  plate  there  is  danger  of  the  high-light 
dots  being  closed  up. 


100 


horgan's  half-tone 


The  shape  of  the  half-tone  dot  is  governed  to  a  great 
extent  by  the  shape  of  the  aperture  in  the  diaphragm,  as  the 
half-tone  dot  is  largely  an  image  of  the  diaphragm  aperture. 
The  half-tone  photographer  can  take  advantage  of  this.  For 
instance,  if  he  wants  a  half-tone  negative  in  single  lines  from 
a  cross-line  screen,  he  can  cut  from  bristol-board  a  dia- 
phragm with  a  slit  opening  at  an  angle  of  forty-five  degrees 
to  its  sides,  which  will  give  a  half-tone  negative  in  single 
lines. 


In  1897  tne  writer  devised  two  stops  for  making  news- 
paper half-tone  negatives,  in  which  the  aim  was  chiefly  great 
contrast.  The  smaller  one,  for  getting  the  shadow  dots,  was 
a  square  stop  set  diagonally,  and  the  larger  one  —  for  closing 
up  the  high  lights  quickly  —  was  a  large  square  stop  with 
the  corners  extended.  They  have  gone  into  general  use  and 
have  been  given  the  writer's  name.  They  are  referred  to 
here  for  the  reason  that  these  stops  have  been  redrawn  by 
several  artists,  when  copied  into  French,  German  and  other 
publications.  Then  they  have  been  recopied  back  into  Eng- 
lish publications  in  such  distorted  shapes  that  the  author  can 
scarcely  recognize  them.  Further,  and  what  is  much  worse, 
they  are  recommended  for  all  half-tone  purposes  when  they 
were  only  intended  to  produce  contrasty  negatives,  for  which 
they  will  be  found  to  be  admirably  adapted. 

Every  conceivable  shape  of  diaphragm  aperture  has  been 
tried  for  normal  half-tone  negative-making  and  the  expe- 


HORGAN  STOPS.' 


AFTER  COLLIDING   WITH   THE  OVERLAND  EXPRESS 

NEWSPAPER  HALF  TONE  BY  AMERICAN  PRESS  ASSOCIATION 


THE  HALF-TONE  PROCESS 


101 


rience  gained  from  their  use  is  that  the  round,  square,  and 
square  with  extended  corner  stops  fulfil  all  requirements. 
Still  half-tone  operators  will  continue  to  construct  their 
favorite  shaped  stops,  and  from  the  wonderful  results  they 
alone  obtain  from  their  use  they  would  seem  to  be  justified. 

HALF-TONE  DEVELOPMENT. 

The  feature  to  be  observed  in  half-tone  development  is 
that  the  developing  solution  be  flowed  over  the  exposed  plate 
so  as  to  cover  it  in  one  sweep.  Stoppage  of  the  flow  of 
developer  is  liable  to  leave  a  line  that  can  not  afterward  be 
eliminated. 

Should  the  sensitive  plate,  from  long  exposure,  become 
too  dry,  it  can  be  dipped  once  more  in  the  silver  bath.  This 
supplies  the  surface  with  the  free  silver  which,  combining 
with  the  iron  of  the  developer,  forms  the  intense  image 
desired.  Drying  of  the  plate  from  long  exposure  may  be 
prevented  by  placing  a  sheet  of  wet,  red,  or  other  color  than 
white,  blotter  behind  the  sensitive  plate  in  the  plateholder 
during  exposure. 

When  fixing  the  plate  with  cyanid  of  potassium  solution 
care  must  be  taken  that  it  is  not  so  strong  that  it  will  dis- 
solve away  the  delicately  graded  fringe  that  surrounds  the 
dots,  for  this  fringe  is  later  to  be  intensified  and  brings  about 
the  joining  of  the  high-light  dots  that  is  so  necessary. 

POINTS  OF  INTENSIFICATION. 

The  half-tone  negative  must  be  washed  well  between 
intensifying  operations  to  prevent  stain.  A  tendency  to 
discoloration  of  the  transparent  parts  of  the  film  can  be 
removed  with  a  weak  solution  of  nitric  or  hydrochloric  acid. 

No  rules  can  be  laid  down  that  will  describe  precisely  the 
intensification  and  "  cutting  "  operations,  for  etchers  are  not 
agreed  as  to  what  constitutes  the  best  half-tone  negative. 
Some  etchers  insist  on  what  they  call  a  "  fat "  high-light  dot 
in  the  print  on  metal  so  as  to  allow  for  its  reduction  during 
etching.  The  higher-skilled  etcher  can  use  a  negative  that  is 
not  so  flat  but  has  more  of  the  gradations  of  the  original 


102 


horgan's  half-tone 


copy.  One  point  etchers  do  agree  upon,  and  that  is  that  the 
finer  the  needle-point  dots  in  the  deepest  shadows  the  better, 
for  the  tendency  is  to  enlarge  these  dots  as  the  etching  pro- 
ceeds and  thus  flatten  the  result. 

HALF-TONE  ENAMEL. 

The  sharp  smooth-edged  character  of  the  relief  half-tone 
dots  on  copper  is  due  to  the  acid  resist  used,  which  is  called 
"  enamel "  because  —  like  the  enamel  on  a  watch-dial,  the 
enamel  on  leather,  or  true  enamels  —  it  is  applied  to  the  metal 
plate  while  in  solution  and  by  the  application  of  heat  dries 
with  a  hard,  smooth,  glossy  surface  which  is  a  splendid 
resistant  of  the  chlorid  of  iron  used  to  dissolve  away  the 
copper. 

The  enamel  used  on  a  metal  plate,  usually  copper,  is  com- 
posed of  a  fish-glue,  with  the  addition  of  albumen  or  other 
colloid,  and  made  sensitive  to  light  with  ammonium  bichro- 
mate and  sometimes  chromic  acid.  It  is  a  simple  mixture 
which,  when  intelligently  handled,  will  give  least  trouble  of 
all  the  processworker's  solutions. 

Here  is  a  formula  that  has  been  found  reliable,  during 
years  of  use,  under  all  kinds  of  conditions : 


Water    5  ounces 

Le  Page's  glue  1^2  ounces 

Albumen,  from  a  fresh  egg   1  ounce 

Ammonium  bichromate  100  grains 

Aqua  ammonia  (about)   12  drops 


The  clarified  glue  varies  in  the  proportion  of  water  it 
contains.  It,  as  well  as  the  enamel,  should  be  kept  in  a  cool 
place  and  used  always  at  the  same  temperature,  for  it  will  be 
found  to  be  thicker  as  the  temperature  lowers  and  thinner  as 
the  temperature  rises. 

Albumen  is  not  necessary  to  form  an  enamel.  It  increases 
the  sensitiveness,  though,  and  aids  in  the  development  of  a 
cleaner  and  sharper  print.  Enamel  containing  albumen  will 
work  best  when  one  or  two  days  old,  but  will  spoil  within  a 
week  if  not  kept  on  ice. 

A  thick  coating  should  have  proportionately  less  bichro- 


MEZZOGRAPH  SCREEN. 
The  first  photoengraver,  Joseph  Nicephore  Niepce. 
The  Cincinnati  Process  Engraving  Company,  Cincinnati. 


THE  HALF-TONE  PROCESS 


103 


mate  than  a  thin  one,  for  the  reason  that  the  enamel  must  be 
acted  upon  by  light  through  to  the  copper  in  order  that  it 
may  not  wash  away  in  development.  The  orange  color  of 
the  enamel  is  a  strong  color  filter,  to  prevent  light  from  pene- 
trating and  hardening  the  enamel  in  contact  with  the  copper, 
and  this  is  just  where  the  enamel  should  be  most  impervious 
to  water.  The  orange-colored  enamel  coating  is  specially 
resistant  to  the  blue-violet  rays  of  an  enclosed  arc  electric 
light,  so  that  where  such  lamps  are  used  the  enamel  coating 
should  be  thin. 

The  addition  of  ammonia  renders  the  solution  more  light- 
absorbent  by  changing  its  color  from  an  orange  to  a  pale 
yellow.  Also,  by  neutralizing  the  solution,  it  preserves  it  in 
working  condition  longer.  Where  chromic  acid  is  used, 
ammonia  changes  some  of  the  chromic  acid  to  a  chromate  of 
ammonia. 

PREPARING  THE  COPPER  FOR  ENAMEL. 

That  the  enamel  acid  resist  may  stick  during  etching 
depends  to  a  great  extent  on  the  preparation  of  the  copper 
surface.  All  trace  of  oil  or  grease  used  in  the  machine 
grinding  and  polishing  of  the  copper  must  be  removed 
by  warming  the  metal  and  brushing  over  its  surface  some 
clean  caustic  potash  in  solution,  or  by  scrubbing  the  surface 
with  whiting  moistened  with  water  containing*  a  little  caustic 
potash.  It  is  customary  to  go  over  the  surface  of  the  copper 
with  willow  charcoal  to  remove  the  burnished  surface  and 
give  the  metal  a  slight  tooth  to  hold  the  enamel  better.  This 
polishing  with  charcoal  should  be  done  with  clean  water  and 
in  the  direction  of  the  machine  polish.  Wash  off  with  a  wad 
of  clean  cotton  or  a  sponge  any  adhering  charcoal  or  other 
cleaning  powder,  and  then  the  cleaned  copper  is  ready  for  - 

COATING  WITH  ENAMEL. 

After  mixing  the  enamel  it  is  filtered  a  couple  of  times 
through  a  pledget  of  filtering  cotton  in  the  neck  of  a  glass 
funnel,  taking-  care  that  no  bubbles  are  formed  in  the  filtered 
solution. 


104 


horgan's  half-tone 


While  the  copper  plate  is  still  wet  with  clean  water  it  is 
flowed  with  the  enamel  and  the  first  coating  allowed  to  flow 
off  in  the  sink.  The  second  coating  may  also  go  to  waste. 
The  third  or  fourth  coating,  providing  it  contains  no  dirt 
specks  or  air  bubbles,  should  be  retained  while  the  plate  is 
quickly  fastened  in  the  whirler  and  revolved  at  such  speed 
as  is  found  by  experiment  to  give  the  proper  thickness  of 
coating.  This  whirling  is  usually  done  in  a  circular  drum  or 
tank  to  catch  the  surplus  enamel  that  flies  from  the  edges  of 
the  plate.  At  the  bottom  of  this  drum  is  a  circle  of  low- 
burning  gas  jets,  or  a  gas  stove  covered  with  an  iron  plate, 
from  which  the  heat  arises  to  dry  the  enamel  coating. 

PRINTING  AND  DEVELOPING  ENAMEL. 

When  bringing  the  negative  and  enamel-coated  copper 
together,  care  must  be  taken  that  they  are  of  the  same  tem- 
perature or  a  sweat  may  be  formed  upon  the  enamel.  The 
printing- frame  is  one  made  for  the  purpose.  The  proper 
period  of  exposure  can  be  found  only  by  trial.  With  a  prop- 
erly intensified  negative  there  is  not  much  danger  of  over- 
exposure. 

When  the  exposed  copper  plate  is  removed  from  the 
frame  it  is  laid  in  a  tray  of  clean  water  to  permit  the  glue 
unhardened  by  light  to  soften.  This  will  require  a  minute  or 
more,  when  the  plate  is  placed  under  the  tap  and  a  strong  jet 
of  water  allowed  to  fall  upon  it,  which  washes  away  the 
softened  enamel.  There  is  in  a  good  light,  sufficient  differ- 
ence between  the  brown  shade  of  the  light-hardened  glue 
and  the  pink  of  the  bared  copper  to  tell  when  the  image  is 
developed  clean.  The  best  operators  do  not  dye  the  enamel 
to  determine  when  the  development  is  finished. 

Should  a  dye  be  considered  necessary,  methyl  violet  is  the 
one  most  commonly  used.  A  weak  solution  of  it  is  poured  on 
and  off  the  developed  image,  which  it  quickly  stains.  The 
writer  has  found  an  anilin  dye  called  "  cotton  blue  "  to  give  a 
better  color  contrast  to  the  copper,  and  when  enamel  stained 
with  it  is  flowed  over  with  a  weak  solution  of  alum  it  changes 


DUOGRAPH. 


Using  half-tone  and  mezzograph  screens. 
Gatchel  &  Manning,  Philadelphia,  Pa. 


THE  HALF-TONE  PROCESS 


105 


in  color  to  a  most  brilliant  blue.  All  anilin  stains  disappear 
as  the  enamel  is  being  burned  in. 

Overexposure,  shown  by  slight  traces  of  glue  in  the 
shadow  dots,  can  be  overcome  by  pouring  on  these  dots 
slightly  warmed  water,  and  spots  requiring  further  develop- 
ment can  be  "  tickled  "  clear  by  drawing  over  them  wet 
cotton.  Development  being  completed,  the  enamel  is  dried, 
in  sunlight  when  possible. 

BURNING  THE  ENAMEL. 

Or,  the  copper  plate  is  gripped  with  a  wide-nosed  pliers 
and  moved  over  a  proper  gas  stove  until  the  moisture  is 
slowly  evaporated  out  of  the  enamel  image ;  then  the  heat  is 
increased  and  the  changing  colors  of  the  enamel  watched  so 
that  by  moving  the  plate  it  will  be  heated  alike  over  its  whole 
surface.  As  the  heat  of  the  copper  increases  the  color  of  the 
enamel  changes  from  a  yellow  to  a  brown,  gradually  becom- 
ing darker  until  it  reaches  a  deep  chocolate,  which  indicates 
that  the  enamel  is  sufficiently  carbonized.  A  thin  enamel 
coating,  which  is  best  for  fine  work,  will  not  burn  to  as  dark 
a  color  as  a  thick  coating.  Enamel  containing  chromic  acid 
can  be  burned  almost  to  a  black.  When  the  enamel  is  dark 
enough  the  exposed  copper  usually  changes  in  part  to  a  sil- 
very hue.  The  heated  copper  is  now  stood  against  a  wall  to 
allow  air  to  circulate  around  the  hot  copper  plate,  and  cool 
it  evenly.  Under  no  circumstances  plunge  it  in  water  or 
lay  it  on  a  cold  slab,  as  sudden  cooling  destroys  the  temper 
of  the  copper. 

TO  REMOVE  SCUM. 

When  the  developed  plate  is  first  put  into  the  etching 
solution  it  will  be  found  that  there  are  some  portions,  par- 
ticularly in  the  fine  shadow  dots,  that  are  not  attacked  by  the 
iron  solution ;  this  is  due  to  a  slight  veil  of  enamel  covering 
the  copper  in  these  parts,  which  is  termed  "  scum."  And  so 
common  is  it  that  most  etchers  apply  an  agent  for  removing 
any  possibility  of  scum  before  they  attempt  to  etch  the  plate. 


106 


horgan's  half-tone 


Among  the  various  suggestions  for  scum  removal  the  follow 
ing  solution  will  be  found  efficient : 


Another  solution  used  is  similar  to  the  above  except  that 
acetic  acid  is  substituted  for  the  hydrochloric  acid.  Either 
solution  is  applied  and  with  a  brush  scrubbed  vigorously 
over  the  enamel  image  until  the  copper  shows  bright 
everywhere.  The  plate  is  rinsed  quickly  under  the  tap 
and  plunged  into  the  iron  etching  fluid. 


Copper  etching  is  a  much  simpler  operation  than  three- 
bite  zinc  etching  after  one  has  confidence.  Most  failures 
occur  from  timidity,  for  the  reason  that  with  a  vigorous, 
quick  etching  with  chlorid  of  iron  there  is  little  danger  of  the 
acid-resisting  enamel  protection  being  injured,  while  the  use 
of  a  weak  etching  solution  and  much  washing  with  water 
will  soften  the  enamel.  It  is  for  this  reason  that  the  quick 
action  of  an  etching  machine  gives  a  more  satisfactory  result 
than  can  usually  be  had  in  the  slowly  rocked  etching  tub. 

Chlorid  of  iron  is  the  most  reliable  etching  fluid.  It  can 
be  purchased  in  a  neutral  solution  at  a  strength  of  about 
400  B.,  or,  the  iron  chlorid  (ferric  chlorid)  can  be  purchased 
in  lumps  and  dissolved  in  hot  water  until,  when  cool,  it  tests 
400  B.  From  370  to  40°  B.  will  be  found  the  best  strength 
for  etching  enamel  protected  copper.  A  mixture  of  old  and 
new  etching  bath  in  the  proportion  of  equal  parts  of  each 
will  etch  smoother  than  an  entirely  fresh  solution  of  chlorid 
of  iron.  A  warm  iron  solution  will  etch  much  faster  than  a 
cold  one. 

If  an  etching  machine  is  not  available,  then  "  still "  etch- 
ing is  recommended.  This  is  done  by  turning  the  plate  face 
down  in  the  chlorid  of  iron  solution,  avoiding  air  bubbles, 
the  corners  of  the  plate  resting  on  supports  which  keep  it  as 
far  from  the  bottom  of  the  tray  as  possible.   The  principle  of 


Water   

Table  salt   

Hydrochloric  acid 


20  ounces 


4  ounces 
2  ounces 


HALF-TONE  ETCHING. 


THE  HALF-TONE  PROCESS 


107 


this  method  of  etching  is  that  the  iron  solution  dissolves  the 
copper  and  both  fall  to  the  bottom  of  the  tray  while  fresh 
etching  fluid  rushes  in  to  take  their  places.  It  dispenses  with 
brushing  to  clear  the  etched  parts  of  oxid,  and  there  is  not  so 
much  danger  of  undercutting  as  when  the  etching  tub  is 
rocked  and  the  iron  solution  is  dashed  against  the  sides  of 
the  dots. 

When  a  copper  plate  is  etched  in  a  rocking-tub  it  should 
be  turned  occasionally  and  brushed  as  little  as  possible,  for 
when  brushing  out  the  oxid  that  adheres  to  the  bottom  of  the 
fine-shadow  dots  there  is  a  tendency  to  open  up  these  intaglio 
dots  and  gray  the  result.  As  the  etching  approaches  the 
proper  depth  the  fine  isolated  dots  in  the  extreme  high  lights 
are  usually  undercut,  so  that  the  enamel  protection  is  held 
only  in  the  center  like  an  umbrella.  This  is  a  warning  to 
stop.  On  examining  the  dots  with  a  magnifier  do  not  wash 
the  iron  solution  from  the  plate;  blow  it  from  the  spot  to 
be  examined.  When  the  etching  is  completed,  water  can  be 
applied  to  the  enamel  for  the  first  time  since  the  scum  was 
removed.  After  washing,  the  adhering  water  is  absorbed  by 
dabbing  the  surface  with  a  dampened  piece  of  chamois-skin 
and  the  plate  is  dried  by  heat. 

The  enamel  is  then  gone  over  with  a  dry  nail-brush, 
which  removes  the  umbrella-shaped  fringes  from  the  dots ; 
the  etching  is  rubbed  full  of  magnesia,  which  fills  in  the 
etched  portions  and  shows  the  actual  state  of  the  etching. 

HALF-TONE  FINISHING  OR  REETCHING. 

Sometimes  copper  half-tones  are  only  flat-etched  in  the 
tub  or  machine.  That  is  they  are  etched  until  the  shadows 
are  right  in  tone,  the  lighter  tones  and  high  lights  being 
reduced  to  their  proper  fineness  by  the  engraver  called  a 
finisher.  His  method  is  to  protect  with  asphalt  or  shellac 
varnish  the  shadows,  or  areas  sufficiently  etched,  and  then, 
with  a  bamboo-handled  Chinese  marking  brush,  paint  chlorid 
of  iron  solution  on  the  high  lights,  gradually  spreading  it 
over  the  darker  tones,  until  the  dots  in  those  portions,  so 
covered  with  iron,  are  reduced  to  print  light  enough.  The 


108 


horgan's  half-tone 


iron  solution  is  absorbed  from  the  etched  surface  with  pieces 
of  blotter.  This  work  requires  great  skill  and  artistic  judg- 
ment on  the  part  of  the  finisher,  who  usually  is  one  who  has 
been  trained  as  a  wood  engraver.  He  has  the  copy  from 
which  the  half-tone  negative  was  made  before  him  as  he 
proceeds  with  the  reetching.  On  the  manner  with  which  he 
usually  improves  on  the  copy  depends  the  quality  of  the  half- 
tones produced  and  the  reputation  of  the  house  by  which  he 
is  employed. 

VIGNETTING. 

Vignetting  is  usually  done  by  the  engraver-finisher,  who 
first  fills  in  the  half-tone  with  magnesia  and  indicates  with  a 
pencil  outline  on  it  where  the  dots  should  fade  away  so  as  to 
be  no  longer  seen.  Outside  of  this  line  he  covers  the  dots 
with  the  asphalt  or  shellac  varnish.  When  the  varnish  is 
dry  he  proceeds  to  paint  chlorid  of  iron  solution  on  the  dots 
nearest  the  edge  of  the  varnish,  gradually  encroaching  on  the 
image.  When  the  iron  solution  has  exhausted  itself  it  is 
absorbed  with  a  piece  of  blotter  and  fresh  iron  solution 
painted  on  as  before.  These  operations  are  repeated  until  the 
enamel  begins  to  disappear  from  the  pin-pointed  dots  at  the 
extreme  edges,  when  the  plate  is  washed  off.  To  remove 
the  stain  the  acid  and  salt  solution,  used  for  scum  removal, 
will,  when  brushed  over  it,  brighten  up  the  whole  plate. 
After  washing  and  drying,  the  plate  is  turned  over  to  the 
router. 

After  routing,  the  outer  edges  of  the  vignetted  plate 
may  be  chamfered  on  the  under  side  so  as  to  lower  the 
printing  surface  when  blocked.  This  requires  but  a  very 
slight  bevel  from  the  outer  edge  to  about  a  quarter  inch 
deep  on  the  under  side  of  the  vignetted  plate. 

PROVING,  BEVELING,  ROUTING,  BLOCKING. 

Proving  is  done  before  the  plate  is  mounted,  for  the 
reason  that  it  can  be  underlaid  and  also  to  prevent  the 
wooden  blocks  from  being  soiled.  This  is  the  work  of  a 
pressman  and  need  not  be  described  here.   Neither  does  the 


DUOGRAPIT. 

-om  a  daguerreotype  of  Louis  J.  M.  Daguerre,  after  whom  the  first 
photographic  process  is  named. 
Plates  hy  the  Electro-Light  Engraving  Co.,  New  York. 


THE  HALF-TONE  PROCESS 


109 


mechanical  operations  of  routing,  beveling  and  blocking 
require  explanation  in  this  book  devoted  only  to  photo- 
mechanical processwork. 

HALF-TONE  ENGRAVERS  SHOULD  KNOW 

MR.  IVES'  HALF-TONE  ENAMEL  FORMULA. 

Mr.  Ives  says  this  is  his  enamel  formula  for  the  ideal 
half-tone  negative,  which  negative  he  describes  as  a  vig- 
orous one,  where  the  gradation  of  line  and  dot  is  complete, 
and  there  are  no  dots  to  print  out  in  the  shadows,  while  the 
dots  in  the  high  lights  are  sufficiently  fine  and  sharp  without 
any  of  the  whittling  down,  which  may  be  accomplished  by 
fine  etching:  Some  will  wonder  how  I  would,  in  the  etch- 
ing process,  keep  such  fine  dots  in  the  shadows,  which 
would  be  printed  out  by  the  methods  usually  employed. 
Or,  preserve  such  fine  dots  in  the  lights,  which  would  be 
etched  out  in  the  ordinary  course  of  procedure.  To  accom- 
plish this,  I  prefer  a  fish-glue  enamel  without  albumen,  for 
copper  etching,  as  follows : 


Le  Page's  glue   5  ounces 

Bichromate  of  potash   88  grains 

Chromic  acid  (pure)  40  grains 

Aqua  ammonia  (strong)  ifa  drams 

Water   12  ounces 


Dissolve  the  bichromate  in  ten  ounces  of  water,  then 
add  the  glue  and  thoroughly  mix.  Then  the  chromic  acid, 
dissolved  in  two  ounces  of  water,  should  be  added  drop  by 
drop,  while  constantly  stirring,  and  finally  the  ammonia. 
This  solution  keeps  better  than  one  containing  albumen,  and 
though  it  sometimes  goes  wrong  in  a  few  days,  Mr.  Ives 
says  he  has  used  it  with  perfect  success  when  five  months 
old. 

HALF-TONE  IN  HOT  WEATHER. 

To  keep  the  sensitized  wet  plate  moist  in  hot  weather 
during  long  exposures  is  a  problem.  Here  are  a  few  rules 
which,  if  followed,  will  prevent  the  plate  drying:  The 


110 


horgan's  half-tone 


ground  glass  should  always  be  kept  in  the  camera  when 
the  latter  is  not  in  use.  In  the  morning  the  interior  of  the 
camera  box  should  be  wiped  out  with  a  large  damp  sponge 
such  as  is  used  in  washing  carriages.  The  plateholder 
should  be  treated  in  the  same  way.  Place  a  few  folds  of 
wet  cloth  on  a  piece  of  galvanized  wire  netting  inside  the 
camera  box. 

Have  the  darkroom  floor,  tables  and  shelves  scrubbed 
out  once  a  week.  After  the  day's  work  sweep  out  the  dark- 
room thoroughly  and  dust  it  with  a  damp  cloth  or  sponge 
in  the  morning.  After  sensitizing  the  plate,  allow  it  to 
drain  well,  wipe  all  silver  solution  from  the  back  and  par- 
ticularly from  the  top  edge  of  the  glass  plate.  When  the 
sensitive  plate  is  in  the  holder,  place  against  the  back  of 
the  glass  plate  a  piece  of  eighty-pound  blotter  an  inch  or 
so  smaller  all  around  the  plate.  This  blotter  should  be  wet 
but  not  dripping.  The  blotter  should  not  be  white  unless 
a  piece  of  black  cloth  or  paper  is  placed  between  it  and  the 
back  of  the  sensitive  plate,  thus  preventing  reflection  of 
white  light  on  the  sensitive  film. 

INVENTOR  OF  THE  ENAMEL  ACID  RESIST 

Charles  E.  Purton,  working  in  Philadelphia  about  1883, 
is  said  to  be  the  first  one  to  use  gum  arabic  and  fish  glue  to 
coat  a  copper  plate  with  and  afterward  carbonize  the  film 
so  as  to  make  it  acid  resistant. 

In  the  Photographic  News  of  November  4,  1881,  Major- 
General  Waterhouse  described  the  Gamier  process,  in  which 
a  copper  plate  was  coated  with  a  solution  of  two  grams  of 
sugar  and  one  gram  of  bichromate  of  ammonia  in  fourteen 
grams  of  water.  This  coating  was  dried  and  printed  under 
a  positive,  and  dusted  with  an  alkalin  powder,  when  the 
image  showed  plainly.  (This  was  the  origin  of  the  dry- 
enamel  process.)  After  which  the  copper  was  heated  over 
a  flame  until  it  showed  iridescent  colors.  The  sugary  coat- 
ing thus  becomes  hard  in  the  exposed  parts,  but  under  the 
powder  it  is  broken,  powdery  and  permeable  to  acids.  It 
was  then  etched  in  perchlorid  of  iron. 


Fig.  2.—  Three-color  Reproduction,  Red  Impression. 
Negative  made  through  a  green  filter. 


Fio  3. —  Three-color  Reproduction,  Blue  Impression. 
Negative  made  through  an  orange  filter. 


\ 


Fig.  4. —  Three-color  Reproduction,  Yellow-red  Impression. 


Fig.  5. —  Three-color  Reproduction,  Yeli.ow-red-blue  Impression. 


FOUR-COLOR  PROCESS. 
Blocks  by  John  Swain  &  Son,  Ltd.,  London. 


THREE-COLOR  PROGESSWORK, 


AND  ALSO 

THE  MAKING  OF  COLOR  BLOCKS  FOR  FOUR  PRINTINGS. 


Before  undertaking  color  processwork  of  any  kind  it  is 
advisable  to  have  one's  eyes  examined  by  a  specialist  to 
learn  if  there  is  any  defect  in  color  perception.  Color- 
blindness is  more  common  than  is  generally  known,  and  it 
is  only  of  recent  years  that  much  attention  has  been  given 
to  it.  Examination  of  students'  eyes  in  one  of  the  largest 
art  schools  in  the  United  States  showed  that  over  sixty  per 
cent  lacked  normal  color-vision.  More  recent  statistics  prove 
that  women  have  far  better  color  discrimination  than  men. 

Some  eyes  lack  entirely  any  appreciation  of  the  sensa- 
tion of  red,  others  fail  to  distinguish  green,  while  a  few  are 
blind  to  the  violet  sensation.  There  are  degrees  in  the 
defectiveness  of  eyes  to  the  color  sensations,  perfect  color- 
vision  being  rare.  The  nearer  perfect  color-vision  is,  the 
better  will  its  possessor  succeed  at  color  processwork  of  any 
kind. 

THE  FATHERS  OF  THREE-COLOR  PROCESSES. 

The  idea  of  the  three-color  process  may  be  said  to  have 
originated  with  Clerk  Maxwell,  who,  in  1855,  while  an 
undergraduate  at  Trinity  College,  England,  and  but  twenty- 
four  years  of  age,  wrote  this :  "  Here  we  have  a  complete 
system  of  recording  color  by  photography,  but  the  prepara- 
tion equally  sensitive  to  rays  of  every  color  has  not  yet 
been  found.'' 

In  1859,  Louis  Ducos  du  Hauron  began  experiments  in 
three-color  work.  By  1869  he  seems  to  have  mastered  the 
theory  of  the  subject,  for  he  published  a  book,  entitled 
"  Les  Couleurs  en  Photographic    Solution  du  Probleme." 

Henry  Collen  in  England  and  Baron  Ransonnet  in 
Vienna  proposed  in  1865  to  make  three  negatives  from  a 
colored  subject  through  red,  yellow  and  blue  glasses. 

111 


112 


horgan's  half-tone 


Dr.  H.  W.  Vogel  made  three-color  work  possible  by 
discovering  color-sensitizers  for  photographic  plates  and 
setting  forth,  in  1873,  this  principle:  the  color  used  in 
dyeing  the  sensitive  plate  must  be  the  same  color  as  the 
pigment  used  in  printing  the  block  made  from  the  plate. 

Nothing  came  of  Dr.  Vogel's  discovery  until  a  lithog- 
rapher named  Ulrich,  in  Berlin,  attempted  to  put  Dr. 
Vogel's  theory  into  practice.  He  found  by  lithography  it 
was.  necessary  to  introduce  a  fourth  printing,  either  gray 
or  black,  to  get  strength  in  the  shadows.  He  showed  some 
of  his  results  at  the  German  Exhibition  in  London  in  1891 
and  received  a  medal. 

Mr.  Fred  E.  Ives  had  exhibited  a  three-color  half-tone 
print  at  the  Novelties  Exhibition,  Philadelphia,  in  1885, 
but  it  is  to  Mr.  William  Kurtz  we  owe  the  practical  appli- 
cation of  all  the  three-color  theories  that  had  gone  before, 
though  he  lost  his  private  fortune  through  his  experiments. 

The  Engraver  and  Printer,  of  Boston,  in  March,  1893, 
published  a  frontispiece  with  this  title :  "  Photography  in 
Colors.  Taken  from  Nature  by  W.  Kurtz,  Madison  Square, 
New  York.  Printed  in  Three  Colors  on  the  Steam  Press." 
This  was  a  fruit-piece  printed  from  three  single-line  blocks 
and  proved  to  the  whole  printing  world  that  reproductions 
of  colors  by  photography  into  three  half-tone  blocks  to  be 
printed  in  colored  inks  had  arrived. 

THE  THEORY  OF  THE  THREE-COLOR  PROCESS. 

All  three-color  processwork  is  based  on  the  theory  that 
there  are  but  three  primary  colors,  and  that  all  the  other 
colors  or  hues  are  mixtures  of  these  three  in  varying  pro- 
portions. 

Tints  in  three-color  block  printing  are  obtained  by  allow- 
ing exposure,  in  varying  degrees,  of  the  white  surface  on 
which  the  three  colors  are  printed.  Shades  are  the  result  of 
superimposing  the  three-colored  inks  in  dots  on  and  between 
each  other,  until  black  is  reached  by  printing  the  three  colors 
solidly  over  each  other. 


THREE-COLOR  PROCESSWORK 


113 


For  clearness  sake  the  three  colors  used  in  the  printing- 
inks  will  be  called  yellow,  red,  and  blue,  according  to 
Prang's  standard  colors. 

Let  it  be  remembered  that  in  making  a  negative  of  a 
black-and-white  subject,  for  ordinary  photoengraving  and 
printing  in  black  ink,  the  black  in  the  copy  does  not  affect 
the  sensitive  plate;  it  is  represented  by  the  transparent 
part  of  the  negative.  It  is  only  the  white  and  the  lighter 
shades  that  form  the  deposit  in  the  negative,  and  these  are 
not  printed  in  the  printing-press.  It  is  the  same  in  three- 
color  record  negative-making.  The  color  that  is  recorded 
on  a  color-record  negative  is  the  one  that  is  cut  off  by  the 
filter  and  not  allowed  to  reach  the  sensitive  plate,  or,  the 
color  for  which  the  plate  is  insensitive. 

The  theory  is  that  in  making  the  negative  for  the  yellow 
printing-block  the  yellow  in  the  copy  should  not  affect  the 
sensitive  plate,  but  should  be  the  transparent  part  of  the 
negative  and  is  therefore  the  yellow  color-record  negative. 
In  making  the  negative  for  the  red  printing-block  the  red 
in  the  copy  should  not  affect  the  sensitive  plate  but  should 
be  the  transparent  part  of  the  negative.  In  making  the 
negative  for  the  blue  printing-block  the  blue  in  the  copy 
should  be  represented  by  transparency  in  the  negative. 

The  negatives  in  three-color  work  have  no  color  in 
themselves,  but  record  the  amount  and  gradations  of  each 
of  the  three  primary  colors  found  in  that  which  is  photo- 
graphed. Hence  they  are  properly  termed  color-record 
negatives  and  sometimes  color-separation  negatives. 

THEORETICAL    SENSITIVE    PLATES    FOR    THREE-COLOR  WORK. 

To  make  three-color  record  negatives  the  yellow  nega- 
tive should  be  made  on  a  plate  that  is  sensitive  to  red  and 
blue,  and  insensitive  to  yellow;  the  red  negative  should  be 
made  on  a  sensitive  plate  that  is  sensitive  to  yellow  and 
blue,  and  insensitive  to  red;  while  the  blue  negative  should 
be  made  on  a  plate  that  is  sensitive  to  red  and  yellow,  and 
insensitive  to  blue.  Or,  the  color-record  negatives  should 
8 


114 


horgan's  half-tone 


be  made  on  panchromatic  plates,  sensitive  to  all  colors,  by 
filtering  out  with  color  screens  the  colors  to  be  recorded. 

THE  THEORY  OF  THE  COLOR  FILTERS  OR  SCREENS. 

To  aid  in  carrying  out  this  theory,  transparent  colored 
screens  or  filters  are  used.  These  are  transparent  colored 
mediums  through  which  the  rays  of  light  pass  in  going 
from  the  copy  to  the  sensitive  plates.  In  making  the  yel- 
low negative,  a  purple-colored  filter  should  be  used  to  shut 
out  the  yellow  rays  and  allow  only  the  red  and  blue  rays 
to  pass  through;  for  the  red  negative,  a  green-colored 
filter  should  shut  out  the  red  rays  and  permit  the  yellow 
and  blue  rays  to  pass ;  and  for  the  blue  negative,  an  orange- 
colored  filter  should  shut  out  the  blue  rays  and  permit  the 
passage  of  the  yellow  and  red  rays  of  light  from  the  copy. 
So  much  for  the  theory. 

PRACTICE  VERSUS   THEORY   IN   THREE-COLOR  PHOTOGRAPHY. 

In  practice  it  will  be  found  that  neither  color  filters, 
sensitive  plates,  nor  three-color  inks  are  available  to  carry 
on  three-color  block-making  precisely  as  laid  down  theo- 
retically in  the  previous  paragraphs.  Why  this  is  so  is  too 
long  a  story  to  be  told  here.  By  numerous  compromises 
and  skilful  manipulation,  however,  these  difficulties  are  in 
a  measure  overcome,  so  that  in  practice  three-color  blocks 
can  be  produced  which  are  quite  satisfactory. 

Some  establishments  find  that  for  some  subjects  it  is 
better  to  add  a  fourth  plate  to  be  printed  in  gray,  or  a  warm 
or  cold  black.  How  this  fourth  plate  is  made  will  be  told 
when  the  use  of  color  screens  or  filters  is  described. 

THE  LIGHT. 

Daylight  in  or  near  large  cities  and  in  changeable 
weather  is  too  variable  to  furnish  the  best  illumination  for 
three-color  negative-making.  The  color  of  the  light  from 
a  clear  sky,  it  will  be  understood,  is  bluer  than  from  a 
clouded  sky.  So  also  is  the  light  from  the  sun  yellower 
as  it  sinks  in  the  west.  These  variations  in  the  color  of  the 
light  alter  the  colors  in  the  copy,  besides  making  it  almost 


THREE-COLOR  HALF-TONE. 
The  Zeese-Wilkinson  Co.,  New  York. 


THREE-COLOR  PROCESSWORK 


115 


impossible  to  calculate  correctly  the  time  of  exposure  for 
the  three  negatives.  Electric  arc  focusing  lamps  of  a  good 
make,  with  proper  carbons  and  a  steady  supply  of  electric 
current,  furnish  the  most  reliable  light  for  three-color  pho- 
tography. 

Instead  of  using  color  filters  between  the  copy  and  the 
sensitive  plate,  the  copy  itself  can  be  illuminated  with  col- 
ored light.  For  instance,  the  illuminant  may  be  a  powerful 
electric  light  between  which  and  the  copy  colored  screens 
are  introduced.  As  great  care,  however,  will  be  required 
to  have  these  large  light  filters  properly  adjusted  and  main- 
tained as  if  they  were  the  smaller  ones.  As  there  are 
mechanical  difficulties  to  be  overcome,  as  will  be  seen,  this 
plan  is  not  adopted. 

There  are  in  the  market  what  are  called  flaming-arc 
electric  light  lamps  which,  with  special  carbons,  give  a  pow- 
erful light.  These  reduce  the  period  of  exposure  greatly. 
In  some  establishments  electric  searchlights  are  used  to 
illuminate  the  copy  in  colors.  So  many  local  conditions 
enter  into  the  color  of  the  electric  light  —  it  being  influ- 
enced by  the  action  of  the  lamp  itself,  the  quantity  of  cur- 
rent and  the  quality  of  the  carbons  —  that  it  is  impossible 
to  advise  in  this  matter  here. 

THE  LENS  AND  THE  CAMERA. 

The  special  feature  of  the  lens  should  be  its  correction 
for  chromatic  aberration,  so  that  all  colored  rays  passing 
through  the  lens  may  come  to  a  similar  focus  on  the  ground 
glass.  Non-achromatic  lenses  focus  the  violet  rays  nearer 
the  lens  than  the  yellow  rays.  The  violet  rays,  not  being 
visible  on  the  ground  glass,  are  the  ones  that  act  strongest 
on  the  sensitive  plate,  while  the  yellow  rays  are  the  ones 
focused  and  are  slower  to  act  on  the  sensitive  plate  than  the 
violet  ones,  consequently  the  violet  image  on  the  plate  is  out 
of  focus.  Hence,  in  using  a  non-achromatic  lens  it  is  neces- 
sary after  focusing  to  move  the  ground  glass  forward  to 
a  point  where  the  violet  rays  will  be  in  focus. 

When  the  photographic  gelatin  dry  plate  came  into  use, 


116 


horgan's  half-tone 


sensitive  to  the  yellow  rays,  lenses  were  constructed  so  as  to 
bring  the  violet  and  yellow  rays  to  the  same  focus,  and  such 
lenses  were  termed  "  achromatic."  With  some  "  achro- 
matic "  lenses  the  image  will  have  to  be  focused  through  each 
color  filter  used,  or  three  times.  The  difficulty  of  keeping  the 
images  the  same  size  so  as  to  maintain  perfect  register  need 
not  be  pointed  out. 

For  three-color  photography  it  is  essential  that  the  lens 
be  corrected  still  further  so  that  the  red  rays  are  also 
brought  to  the  same  focus  as  the  violet  and  the  yellow  ones, 
such  lenses  are  called  apochromatic,  and  through  the  use  of 
special  Jena  glass  are  now  to  be  had  from  all  makers  of 
first-class  photographic  lenses,  though  it  is  well  to  test  each 
lens  before  purchasing. 

TO  TEST  AN  APOCHROMATIC  LENS. 

A  chart  can  be  carefuly  drawn  consisting  of  outline 
squares,  as  shown  in  the  diagram : 


B 

.Y 

R 

B 

Y 

R 

B 

Y 

R 

Y 

R 

B 

Y 

R 

B 

Y 

R 

B 

R 

B 

Y 

R 

B 

Y 

R 

B 

Y 

B 

Y 

R 

B 

Y 

R 

B 

Y 

R 

Y 

R 

B 

Y 

R 

B 

Y 

R 

B 

R 

B 

Y 

R 

B 

Y 

R 

B 

Y 

B 

Y 

R 

B 

Y 

R 

B 

Y 

R 

Y 

R 

B 

Y 

R 

B 

Y 

R 

B 

R 

B 

Y 

R 

B 

Y 

R 

B 

Y 

CHART  TO  TEST  A  LENS  FOR  COLOR  CORRECTION. 


These  squares  are  drawn  in  outline  in  the  color  indicated 
by  the  letter  in  each  square:  yellow,  red  and  blue.  The 
lines  should  be  made  with  a  ruling  pen,  the  lines  in  the  dif- 


THREE-COLOR  PROCESSWORK 


117 


ferent  colors  being  precisely  the  same  width,  with  the 
squares  the  same  distance  apart.  The  red  ink  can  be  used 
dilute,  but  should  be  free  from  any  trace  of  blue.  The 
chart  can  be  one  and  one-half  times  larger  than  the  largest 
plate  it  is  intended  to  make  with  the  lens,  and  must  be 
focused  on  the  blue  squares. 

A  negative  of  this  chart  made  on  any  of  the  numerous 
isochromatic,  orthochromatic,  polychromatic  or  panchro- 
matic plates  now  on  the  market,  or  on  a  collodion  emulsion 
plate  sensitized  for  red,  will  give  an  idea  of  the  apochro- 
matic  properties  of  the  lens. 

If  any  of  the  squares  are  out  of  focus,  or  if  the  outer 
edges  of  the  squares  do  not  form  a  perfect  line,  as  in  the 
drawing,  then  the  lens  is  not  suitable  for  three-color  record 
negative-making. 

THREE-COLOR  FILTERS  OR  SCREENS. 

The  practical  three-color  worker  should  not  attempt  to 
make  his  own  three-color  filters.  The  makers  of  the  color- 
sensitive  plates  and  collodion  emulsions  have  studied  out 
scientifically  the  color  filters  best  adapted  to  their  own  make 
of  plates  or  emulsions.  It  will  be  a  great  saving  of  time 
and  money  on  the  part  of  the  beginner,  at  least,  if  he  adopt 
the  color  filters  recommended  by  the  maker  of  the  sensitive 
plates  or  emulsions  he  is  using. 

Color  filters  are  made  in  several  forms.  In  all  cases  the 
glass  used  in  them  must  be  optically  flat.  The  most  scientific 
form  of  filter  is  the  glass  cell,  filled  with  an  anilin  dye. 
These  can  be  purchased  with  pipette  for  filling  and  emptying 
them.  In  another  form  of  color  filter  two  optically  flat 
glasses  are  first  coated  with  gelatin,  then  stained  with  the 
proper  dye,  and  when  dry  cemented  together  with  Canada 
balsam.  In  another  a  filtered  collodion  is  substituted  for 
gelatin  as  a  medium  for  holding  the  dye.  Screens  of  col- 
ored films  of  gelatin  or  collodion  are  also  frequently  used. 

The  three-color  filters  are  preferably  used  in  grooved 
slides  immediately  behind  the  back  combination  of  the  lens. 
They  can,  however,  be  used  in  front  of  the  lens.  Screens 


118 


horgan's  half-tone 


of  colored  films  of  gelatin  or  collodion  are  frequently  used 
in  the  slot  of  the  lens  with  the  diaphragm,  though  in  the  end 
it  will  be  found  best  to  use  the  niters  in  a  sliding  carrier 
behind  the  lens. 

These  screens  or  niters  can  be  purchased  from  photo- 
engravers'  supply  houses  anywhere,  or  from  the  makers  of 
dry  plates  and  emulsions. 

TO  MAKE  THE  FOURTH  PLATE. 

The  fourth  printing-plate  is  made  in  several  different 
ways.  Some  use  the  red  filter  and  get  an  overexposed  blue- 
record  negative,  which  is  developed  up  and  intensified  rather 
hard,  and  possibly  "  cut "  a  little  in  the  half-tone  negative. 
Others  make  a  negative  on  an  ordinary  dry  plate  with  a 
piece  of  optically  worked  glass,  the  same  thickness  as  the 
color  screens,  and  in  place  of  them;  or,  a  yellow  filter  to 
cut  out  the  actinic  violet  rays.  Still  another  method  is  to 
bind  the  three  color-record  negatives  together  in  exact  regis- 
ter and  copy  them  with  an  extremely  long-focus  lens,  thus 
getting  a  composite  positive  of  the  shadows  in  all  three 
negatives.  From  this  positive  the  half-tone  for  the  gray  or 
black  printing-plate  is  made. 

No  matter  in  what  manner  the  negative  for  the  black 
printing-plate  is  obtained,  the  print  on  the  metal  is  etched 
up  bright,  leaving  only  the  darkest  places.  The  reetcher  or 
finisher  can  by  his  skill  supply  any  kind  of  a  fourth  plate 
demanded  by  the  copy,  and  what  these  requirements  are 
depends  on  the  subject  and  whether  the  fourth  plate  is  to 
be  printed  in  a  gray  or  a  warm  or  cold  black.  When  a 
fourth  plate  is  used,  the  red  plate  must  also  be  reduced  in 
importance. 

THE  INDIRECT  AND  DIRECT  METHODS. 

There  are  two  methods  in  use  for  three  and  four  color 
block-making.  The  indirect  method  requires  twelve  sep- 
arate photographic  operations  to  produce  a  set  of  three- 
color  blocks,  and  fifteen  or  sixteen  operations  to  secure  a 
set  of  four-color  blocks.    First,  color-record  negatives  are 


THREE-COLOR  PROCESSWORK 


119 


made  from  the  subject  to  be  reproduced  in  color ;  secondly, 
positives  are  made  from  the  color-record  negatives  ;  thirdly, 
from  these  positives  half-tone  negatives  are  made;  and 
fourthly,  from  the  half-tone  negatives,  prints  on  the  metal 
plates. 

By  the  direct  method  the  half-tone  screen  is  used  before 
the  color-sensitive  plates  while  the  light  also  passes  through 
the  color  niters  when  making  the  color- record  negatives, 
so  that  the  latter  are  also  half-tone  negatives,  from  which 
the  printing  is  done  on  the  metal  plates.  The  direct  method 
thus  reduces  for  three-color  blocks  the  photographic  opera- 
tions to  six,  while  it  lengthens  the  time  of  exposure  in  the 
camera  greatly,  owing  to  the  interference  to  light  which  the 
half-tone  screen  and  color  niters  give,  and  the  use  of  a 
prism  to  get  the  negatives  reversed. 

The  indirect  method  gives  much  opportunity  for  retouch- 
ing and  also  for  local  reduction  and  intensification  in  both 
negatives  and  positives  to  correct  faults  in  the  color-record 
negatives.  Reversed  half-tone  negatives  are  made  by 
simply  reversing  the  positive.  That  is  done  by  turning  the 
film  side  of  the  positive  toward  the  lens  when  making  the 
half-tone  negative  from  it.  Formerly,  plates  were  so  insen- 
sitive to  red  that  the  direct  method  was  impossible.  Now 
sensitizers  are  at  hand  by  which  plates  can  be  made  more 
sensitive  to  red  than  to  green. 

SAFE  LIGHT  FOR  DEVELOPMENT. 

The  chief  difficulty  in  developing  red-sensitive  plates  is 
to  get  a  safe  light  to  develop  them  by.  The  makers  of  red- 
sensitive  plates  supply  a  colored  medium  through  which  the 
light  is  to  pass  before  reaching  the  red  plate.  If  one  is 
obliged  to  make  safety  lights,  then  here  is  one  way  to  do  it : 

A  green-blue  darkroom  light  filter  for  developing  red- 
sensitive  plates  can  be  made  in  this  way :  Dissolve  the  sil- 
ver from  two  undeveloped  gelatin  dry  plates  by  leaving  them 
in  hyposulphit  of  soda  until  they  are  perfectly  clear.  Wash 
the  hypo  thoroughly  from  these  plates,  and  when  they  are 
dry  stain  them  with  the  following  dyes :    Make  a  solution 


120 


morgan's  half-tone 


of  naphthol  green  and  acidify  it  with  a  few  drops  of  glacial 
acetic  acid ;  then  make  a  deep  solution  of  methyl  violet  ren- 
dered alkaline  with  a  little  borax.  Lay  one  of  the  dry  plates 
in  the  naphthol  green  dye  and  the  other  in  the  methyl  violet 
dye  until  they  take  up  as  much  of  the  stain  as  possible; 
rinse  in  water  and  dry  them.  When  they  are  dry,  bind 
them  together  with  strips  of  passepartout  binding  and  they 
are  ready  to  be  used  before  the  darkroom  light. 

For  green-sensitive  plates,  a  red  darkroom  light  must  be 
used.  Such  a  filter  can  be  made  with  two  gelatin  dry  plates 
cleared  of  the  bromid  of  silver  with  hyposulphit  of  soda, 
as  in  making  the  green  light  filter.  Soak  one  of  the  gelatin- 
coated  plates  in  sixty  grains  of  rhodamin  dissolved  in  four 
ounces  of  water,  and  soak  the  second  plate  in  four  ounces 
of  water  in  which  eighteen  grains  of  aurantia  was  dissolved, 
while  the  water  is  warm.  This  aurantia  dye  works  better 
when  made  alkalin  with  a  drop  or  two  of  ammonia.  When 
these  stained  plates  are  dry,  bind  together  as  before.  Two 
sheets  of  dark  ruby  glass  bound  together  also  make  a  safe 
light  for  green-sensitive  plates. 

A  most  valuable  instrument  for  testing  the  absorption  of 
color  filters  and  darkroom  lights  is  a  small  spectroscope. 
The  optician  who  supplies  them  will  explain  their  use. 

THE  COLOR-SENSITIVE  PLATES. 

To  make  the  color-record  negatives  it  is  best,  theo- 
retically at  least,  to  use  panchromatic  plates,  sensitive  to 
the  whole  spectrum.  They  should  be  developed  in  the  same 
kind  of  developer,  its  strength  and  temperature  being  the 
same ;  or  they  could  be  developed  together. 

It  would  be  inadvisable  to  recommend  here  any  special 
brand  of  dry  plates,  or  any  special  make  of  collodion  emul- 
sion. There  are  so  many  kinds  now  in  the  market  that  each 
worker  has  plenty  of  choice. 

The  well-known  house  of  A.  W.  Penrose  &  Co.,  Ltd..  of 
London,  has  just  brought  out  a  collodion  emulsion  which  is 
sold  as  a  powder.  The  directions  for  use  are  extremely  sim- 
ple. A  package  of  the  powder  is  put  into  a  gallon  bottle  and  a 


THREE-COLOR  PROCESSWORK  121 

quart  of  alcohol  poured  over  it.  After  shaking  it  for  a 
couple  of  minutes  a  quart  of  ether  is  added,  the  solution 
shaken  until  all  of  the  powder  is  dissolved,  after  which  it 
is  filtered  and  is  ready  for  use.  There  are  five  sensitizers 
that  come  with  this  emulsion:  Sensitizing  for  the  yellow, 
red,  blue,  black,  and  for  ordinary  half-tone  reproduction. 

Our  own  Cramer  Dry  Plate  Works  has  for  many  years 
supplied  most  reliable  color-sensitive  plates.  So  also  has 
Wratten  &  Wainwright,  in  England.  Dr.  E.  Albert's  eoside 
of  silver  collodion  emulsion  popularized  that  method  of 
working,  while  the  emulsion  sold  most  in  this  country  at 
present  is  that  made  by  Sillib  &  Bruckman,  of  Munich. 
Many  of  the  most  successful  photochromotype  workers  in 
this  country  are  now  using  emulsion  successfully,  some  of 
which  they  make  themselves. 

HALATION  IN  THREE-COLOR-RECORD  NEGATIVES. 

Halation,  or  reflections  from  the  back  surface  of  the 
glass  on  which  the  color-record  negative  is  made,  must  be 
guarded  against,  particularly  in  the  negative  made  through 
the  red  screen.  The  makers  of  color-sensitive  plates  furnish 
them  possessing  nonhalation  properties  if  so  ordered.  There 
are  many  nonhalation  backings  on  the  market  which  should 
be  used  as  directed.  They  are  not  as  effective,  however,  as 
a  double-coated  plate  or  one  having  a  substratum  to  prevent 
halation. 

NONHALATION  BACKING. 

A  paste  to  use  on  the  back  of  the  glass  that  will  absorb 
the  light  and  prevent  it  being  reflected  back  into  the  sensitive 
film  is  the  following : 


Any  mucilage  i  ounce 

Caramel   I  ounce 

Burnt  sienna  2  ounces 

Alcohol   2  ounces 


Grind  the  burnt  sienna  in  water,  add  the  mucilage,  stir 
in  the  caramel,  and  lastly  add  the  alcohol.  After  exposure 
this  paste  should  be  wiped  from  the  back  of  the  plate  with  a 


122 


horgan's  half-tone 


damp  sponge.  It  will  not  injure  the  developer,  though  it 
discolors  it. 

RESENSITIZING  DRY  PLATES. 

An  important  factor  in  three-color  record  negative- 
making  is  to  get  a  plate  as  sensitive  to  the  red  as  possible. 
The  first  dye  to  satisfactorily  sensitize  gelatin  dry  plates  to 
the  red  was  cyanin,  and  it  was  used  as  follows : 

Cyanin,  C.  P  6  grains 

Absolute  alcohol  10  ounces 

The  sensitizing  bath  was  made,  as  wanted,  as  follows: 

Of  the  above  stock  solution   I  ounce 

Alcohol  (ninety-five  per  cent)   20  ounces 

Distilled  water  100  ounces 

This  sensitizing  solution  was  filtered  perfectly  into  a  por- 
celain tray,  and  in  an  absolutely  dark  room  dry  plates  were 
allowed  to  soak  in  this  bath  for  about  five  minutes,  when  they 
were  removed  and  stood  up  on  chemically  pure  blotting  paper 
for  fifteen  minutes  to  drain,  after  which  these  plates  were 
bathed  in  the  following  bath  : 

Distilled  water  20  ounces 

Alcohol  (ninety-five  per  cent)   2  ounces 

Aqua  ammonia  ^2  ounce 

After  rinsing  in  this  bath  for  a  minute  they  were  placed 
in  an  absolutely  dark  place  and  dried  by  an  electric  fan  as 
quickly  as  possible. 

PINACYANOL  SENSITIZER  FOR  RED. 

A  most  superior  sensitizer  for  red  is  pinacyanol,  as  it  has 
no  tendency  to  fog  the  plates.  One  grain  of  this  dye  in 
two  ounces  of  absolute  alcohol  makes  a  stock  solution. 
For  a  sensitizing  bath  take  one  ounce  of  this  stock  solution, 
with  thirty  ounces  of  alcohol  and  sixty  ounces  of  distilled 
water.  The  plates  should  be  left  in  this  bath  for  five  min- 
utes and  then  washed  for  three  minutes  in  running  water; 
the  bathing,  drying  and  all  operations  being  carried  on  in 
absolute  darkness. 


THREE-COLOR  PROCESSWORK 


123 


Without  the  use  of  water  in  this  sensitizing  bath,  the 
gelatin  will  absorb  the  alcohol  and  act  as  a  filter,  leaving  the 
pinacyanol  on  the  surface.  Water  carries  the  dye  into  the 
film. 

Plates  treated  with  cyanin  lose  their  sensitiveness  in 
about  thirty  hours,  while  plates  dyed  with  pinacyanol  will 
keep  sensitive  for  weeks,  and  even  then  they  can  be  resensi- 
tized  without  injuring  them. 

For  collodion  emulsion  sensitive  to  red,  one  grain  of 
pinacyanol  is  dissolved  in  two  ounces  of  absolute  alcohol 
and  this  added  to  two  hundred  ounces  of  collodion.  After 
the  collodion  is  flowed  on  a  glass  plate  and  set,  the  excess 
dye  must  be  washed  from  the  surface  of  the  plate  as  with 
gelatin  plates. 

PINACHROME  SENSITIZER  FOR  GREEN. 

A  most  successful  sensitizer  for  green  is  pinachrome, 
used  in  the  same  manner  as  pinacyanol,  the  bath  being  of 
the  same  strength,  the  bathing  of  the  plate  for  the  same 
length  of  time  as  well  as  the  washing  and  drying.  The  only 
change  is  that  the  operations  are  performed  in  a  weak  red 
light,  as  described  under  "  Safe  Light  for  Development." 

Erythrosin,  or  what  the  Actien  Gesellschaft  fur  Anilin 
Fabrikation  of  Berlin  calls  Tetraiodofluorescein,  is  also  a 
good  sensitizer  for  green.  The  sensitizing  bath  can  be  made 
up  as  follows :  First  make  a  stock  solution  of  ten  grains 
of  erythrosin  in  ten  ounces  of  ninety-five  per  cent  alcohol. 
One  ounce  of  this  stock  solution  is  used  in  fifteen  ounces 
of  distilled  water  with  one  dram  of  ammonia.  This  bath 
should,  like  all  sensitizing  baths,  be  carefully  filtered  before 
using.  The  bathed  plates,  when  washed  for  five  minutes 
in  running  water  and  dried  in  the  dark  as  quickly  as  pos- 
sible, will  keep  for  several  months. 

The  dyeing  and  washing  operations  are  best  carried  out 
by  using  one  of  the  makes  of  cages  found  in  the  market  for 
washing  a  dozen  or  more  dry  plates  by  lowering  them  into 
an  upright  bath,  which  should  contain  the  resensitizing 
solutions. 


124 


HORGAN  S  HALF-TONE 


It  is  preferable  to  perform  these  resensitizing  operations 
in  the  evening  or  the  last  thing  in  the  afternoon  so  that  the 
plates  may  be  ready  for  use  in  the  morning.  It  is  better 
also  to  resensitize  only  sufficient  plates  for  use  during  one 
day. 

The  important  points  to  remember  in  resensitizing  dry 
plates  are :  The  cyanin  must  be  pure,  and  absolute  alcohol 
must  be  used  to  dissolve  it  in ;  the  same  proportion  of  alco- 
hol must  be  used  in  the  washing  bath  that  is  used  in  the 
dyeing  bath ;  that  these  cyanin  plates  will  not  keep  long  and 
that  they  must  be  developed  in  the  dark  at  first,  for  a  min- 
ute or  so,  and  then  in  a  safe  light,  which  should  be  a 
reflected,  not  a  direct  light.  * 

To  determine  if  the  darkroom  light  is  safe  for  resensi- 
tized  plates,  put  a  cyanin-dyed  plate  into  a  plateholder  while 
in  absolute  darkness,  pull  the  slide  of  the  plateholder  half- 
way out  and  expose  the  plate  to  the  darkroom  light  for 
from  three  to  five  minutes.  Develop  this  plate  first  in  the 
dark,  as  before  instructed,  and  see  if  there  is  not  a  trace 
of  exposure  on  the  half  which  was  uncovered  to  the  dark- 
room light.  This  experiment  will  also  determine  whether 
or  not  the  plates  are  going  to  fog  later. 

The  manufacturers  of  anilin  dyes  employ  photographic 
chemists  who  will  supply  the  color-plate  maker  with  infor- 
mation regarding  the  latest  sensitizers  for  collodion  emulsion 
and  dry  plates  and  also  how  to  use  them. 

THE  EXPOSURE. 

The  relative  exposures  can  be  found  only  by  experiment, 
for  they  depend  chiefly  on  the  illumination,  the  lens,  the  dia- 
phragm, the  intensity  of  the  color  filters,  the  sensitiveness 
of  the  plates  used,  and  the  reduction  or  enlargement  of  the 
copy. 

It  is  earnestly  recommended  that  the  photographer 
making  three-color  record  negatives  keep  a  daybook  in 
which  is  registered,  for  every  exposure,  the  subject,  kind  of 
sensitive  plate  used,  reduction  or  enlargement,  lens,  kind 
and  size  of  diaphragm,  color  filter,-  quality  of  illumination 


THREE-COLOR  PROCESSVVORK 


125 


and  length  of  exposure,  together  with  any  other  data  affect- 
ing the  negative.  Later,  the  kind  of  developer,  its  tempera- 
ture, time  of  development  and  comments  on  the  resulting 
negative  should  be  added.  This  daily  register  will  become 
one  of  the  most  valuable  books  of  reference  to  the  photog- 
rapher. It  will  save  much  needless  experimenting  and  waste 
of  time  and  material. 

Strips  of  paper  containing  three  patches  of  color,  cor- 
responding with  those  used  in  the  printing  inks,  together 
with  patches  of  gray,  black,  and  white  are  fastened  along- 
side of  the  "  copy  "  and  included  in  each  negative  made. 
The  object  of  the  patches  of  gray,  black,  and  white  is  to 
show  when  the  negatives  are  properly  timed.  When  the 
gray  patch  approximates  the  same  density  in  each  of  the 
three  negatives  the  ratio  of  exposure  is  correct,  though 
it  must  be  remembered  that  a  plate  bathed  in  a  dye  will  not 
develop  as  intense  a  negative  as  an  unbathed  plate.  There- 
fore the  gray  patch  in  the  yellow  record  negative  will 
develop  more  intense  than  the  similar  patch  in  the  red  and 
blue  record  negatives. 

THE  HALF-TONE  DIAPHRAGM. 

If  from  a  single  half-tone  three  impressions  were  made, 
one  in  yellow  ink,  the  second  in  red  ink  and  the  third  in  blue 
ink ;  if,  also,  the  register  was  so  perfect  that  these  impres- 
sions were  printed  exactly  over  each  other,  the  result  of 
the  three  superimposed  printings  would  appear  like  a  single 
impression  in  black  ink.  Should  these  printings  be  repeated 
and  the  impressions  be  out  of  register,  as  they  are  most  likely 
to  be,  then  varying  color  effects,  called  moire,  will  appear  in 
the  proofs. 

To  prevent,  as  far  as  it  is  necessary,  the  different  inks 
from  printing  over  each  other,  and  to  avoid  these  accidental 
color  effects,  it  was  formerly  considered  necessary  to 
engrave  the  half-tones  in  lines,  so  that  they  could  be  printed 
at  angles  of  sixty  degrees  to  each  other.  Later  it  was  found 
better  to  get  cross-line  effects  in  the  shadows,  lines  in  the 


126  horgan's  half-tone 

half-tones  and  dots  in  the  high  lights.  To  accomplish  this 
with  cross-line  screens  elliptical  diaphragms  were  used. 


ELLIPTICAL  DIAPHRAGMS. 


These  diaphragms  should  be  cut  out  of  printers'  press- 
board  or  ferrotype  plate,  with  the  points  of  the  slits  at 
angles  of  forty-five  degrees  to  the  vertical  sides  of  the  dia- 
phragm, as  shown  in  the  illustration. 

When  in  use,  these  diaphragms  must  be  exactly  in  line 
with  one  of  the  lines  of  the  half-tone  cross-line  screen.  To 
insure  this,  the  plateholder  containing  the  cross-line  screen 
should  be  put  into  its  place  in  the  camera,  a  piece  of  ground 
glass  substituted  for  the  sensitive  plate,  and  the  lens,  con- 
taining one  of  the  elliptical  diaphragms,  turned  until  the 
image  of  the  slot  in  the  diaphragm  makes  continuous  lines 
on  the  ground  glass.  If  the  lens  is  fixed  in  this  position 
this  test  as  to  parallelism  of  the  elliptical  stop  and  one  of 
the  lines  in  the  screen  need  not  be  repeated. 

To  use  these  stops,  more  than  one-half  the  exposure 
may  be  given,  the  lens  capped,  the  diaphragm  reversed  and 
the  remainder  of  the  exposure  made;  or,  a  large  elliptical 
stop  may  be  used  to  close  up  the  high-light  dots  in  the  nega- 
tive, and  a  small  elliptical  stop,  turned  in  the  opposite  direc- 
tion to  the  large  one,  to  furnish  the  small  dots  in  the  shadows 
of  the  negative. 

Another  plan  is  to  use  these  elliptical  diaphragms  with- 
out reversing,  the  effect  in  the  half-tone  being  the  same  as 
if  a  single-line  screen  were  used. 

The  reader  is  presumed  to  be  familiar  with  the  half-tone 


THREE-COLOR  PROCESSWORK 


127 


process ;  it  is  only  necessary  to  refer  here  to  the  additional 
operations  in  the  making  of  three-color  blocks. 

TO  PREVENT  PATTERN  IN  PRINTING. 

In  Richmond's  "  Grammar  of  Lithography/'  pages  170- 
171,  ninth  edition,  1886,  will  be  found  instructions  for  lay- 
ing down  line  tints  for  color-printing  in  three  colors,  in 
which  it  is  stated :  "  The  direction  of  this  second  series  of 
lines  is  very  important,  and  must  make  an  angle  of  sixty 
degrees  with  those  first  transferred.  The  third  transferring 
is  then  done,  and  the  result  should  be  that  the  lines  coincide 
in  direction  with  the  three  sides  of  an  equilateral  triangle. 
The  reason  for  putting  the  lines  so  exactly  in  this  direction 
is  that  the  production  of  any  set  pattern  is  thus  avoided." 


SCREEN  ANGLES  FOR  THREE-COLOR  WORK. 


Ives  used  this  disposition  of  lines  in  his  three-color 
block  of  1881.  Apparently  without  knowing  this,  Albert, 
in  Germany,  patented  the  use  of  lines  at  sixty  degrees  to 
each  other  in  1891 ;  Du  Hauron,  unaware  of  its  having 
been  used  before,  received  a  patent  on  it  in  France  in  1892, 
and  Kurtz,  thinking  it  an  original  discovery  with  himself, 
obtained  a  United  States  patent  on  it  in  1893. 


128 


horgan's  half-tone 


So  the  angle  of  sixty  degrees,  which  lithographers  found, 
generations  ago,  to  be  necessary  in  laying  down  tints,  is  the 
proper  one  for  the  three-color-block  maker  of  to-day. 

The  screenmakers  furnish  two  cross-line  screens  for 
three-color  half-tones  that  are  well  worth  adopting.  One  is 
the  ordinary  cross-line  screen  ruled  with  lines  at  forty-five 
degrees  to  its  sides.  The  other  is  a  special  screen  made  to 
match  the  first  one  both  as  to  thickness  of  lines  and  the 
spaces  between  the  lines.  The  lines  of  the  second  screen 
are  ruled  at  angles  of  seventy-five  and  105  degrees  to  its 
sides.  This  screen  can  be  used  one  way  for  the  yellow 
printing  block  and  reversed  for  the  red  printing  negative. 
Owing  to  this  reversal  the  two  glasses  of  which  the  screen 
is  composed  should  be  of  the  same  thickness. 

The  best  plan  of  all  to  produce  half-tone  negatives,  with 
one  line  thicker  than  the  other,  is  not  to  depend  on  the  uncer- 
tainty resulting  from  timing  the  changes  in  the  elliptical 
stop  but  to  have  the  cross-line  screen  itself  engraved  with 
lines  of  different  thicknesses.  In  this  way  round  stops  may 
be  used,  and  in  every  negative  made  with  it  one  of  the 
crossed  lines  will  preponderate.  Should  a  half-tone  be 
required  from  such  a  screen  with  the  crossed  lines  of  equal 
thickness,  recourse  may  be  had  to  the  elliptical  stops  again, 
and  by  giving  the  greater  exposure  with  stop  turned  in  the 
direction  of  the  thin  line,  normal  half-tone  screen  effects 
can  be  had. 

CAMERA  WITH  CIRCULAR  SCREEN. 

A  more  satisfactory  way,  and  one  necessary  in  the  direct 
method,  to  get  the  screen  angles  in  colorwork  just  right,  is 
to  use  a  circular  screen  in  a  camera  constructed  purposely 
for  colorwork.  Such  a  screenholder  has  the  degrees  clearly 
marked  so  that  the  precise  angles  can  be  had  quickly  and 
with  absolute  certainty. 

As  to  the  angles  for  four-color  printing  blocks,  it  has 
been  found  best  to  retain  the  angles  of  the  stronger  color  — 
black  or  gray,  blue  and  red  at  thirty  degrees  separation, 
and  introduce  the  yellow  at  fifteen  degrees  between  any  two 


REPRODUCTION  OF  AUTOCHROME  IN  FOUR  PRINTINGS 
By  J.  Horace  McFarland  Company 


THREE-COLOR  PROCESS  WORK 


129 


of  them.  Many  four-color  block  makers  use  a  mezzograph 
screen  for  the  yellow  printing  block,  thus  avoiding  danger 
of  a  moire  pattern. 

THE  PROCEDURE  IN  THREE-COLOR  BLOCK  MAKING. 

The  previous  chapters  have  told  of  the  necessity  of  an 
apochromatic  lens  to  bring  the  red,  yellow  and  blue  rays  to 
precisely  the  same  focus.  It  has  been  recommended  to  pur- 
chase color  filters,  or  screens,  darkroom  lights  and  sensitive 
plates,  or  emulsions.  It  is  also  better  to  depend,  for  instruc- 
tions in  the  development  and  handling  of  whichever  brand 
of  plate  that  is  used,  on  the  dry-plate  maker.  Instructions 
for  using  collodion  emulsion  are  usually  given  by  those  who 
supply  it.  Just  how  to  resensitize  dry  plates  for  special 
sensitiveness  to  the  red  has  been  carefully  described.  The 
danger  of  halation,  the  necessity  of  a  reliable  source  of 
illumination  for  the  copy,  and  the  value  of  a  register  of  the 
exposures  and  after-treatment  has  been  urged.  How  to 
make  the  diaphragms  and  the  kind  of  half-tone  screens  and 
camera  to  be  used  has  been  pointed  out.  Having  all  these 
requisites  we  will  now  go  over  the  operations  in  making 
three-color  blocks  by  the  indirect  method. 

We  will  assume  that  a  water-color  sketch  is  to  be  repro- 
duced in  color.  Everything  about  the  camera  must  be  fixed 
firmly  so  that  there  shall  be  no  change  in  the  relative  posi- 
tion of  either  copy,  lens,  or  sensitive  plates  during  the 
making  of  either  negatives  or  positives.  Remember  to  have 
patches  of  the  three  colored  inks,  to  be  afterward  used  in 
the  printing,  as  well  as  patches  of  white,  gray  and  black, 
attached  to  the  copy,  so  as  to  be  photographed  in  each  nega- 
tive.  Also  have  registry  marks  at  all  four  sides  of  the  copy. 

EXPOSING  THE  COLOR-RECORD  NEGATIVES. 

The  blue-violet  filter  is  cleaned  and  inserted  in  its  slide 
behind  the  lens,  and  the  copy  focused  to  its  proper  size. 
Diaphragm  the  lens  down  until  the  image  is  sharp  on  the 
ground  glass  at  every  point.  Cap  the  lens  and  insert  the 
holder  containing  the  blue-sensitive  dry  plate,  draw  the 
slide  one-third  the  distance,  and  expose  the  plate  for  what 

9 


130 


HORGAN  S  HALF-TONE 


might  be  considered  one-half  the  time  required  for  the  whole 
exposure.  Cap  the  lens  again,  draw  the  slide  out  two-thirds 
of  the  way,  and  expose  for  the  same  period  of  time  as  the 
first;  then  draw  the  slide  out  entirely,  and  expose  once 
more  for  the  same  length  of  time.  Do  not  fail  to  make  a 
record  of  all  this  in  the  daily  register.  Development  of  this 
test  plate  will  give  an  idea  of  the  proper  exposure  for  future 
plates.  Repeat  this  time  of  exposure  test  with  the  green 
filter  on  the  green-sensitive  plate  and  on  the  red-sensitive 
plate  with  the  red  filter. 

The  exposure  through  the  green  screen  is  liable  to  be 
longer  than  through  the  blue-violet  screen,  while  the  expo- 
sure through  the  red  screen  may  be  less  than  the  exposure 
through  the  green  screen,  if  the  red-sensitive  plate  has  been 
bathed  in  pinacyanol. 

The  relations  of  the  exposures  vary,  as  has  been  said 
before,  with  the  illumination  of  the  copy,  as  well  as  the  kind 
of  copy,  its  reduction  or  enlargement,  the  density  of  the 
color  filters,  the  kinds  of  plates  used,  whether  collodion 
emulsion  or  gelatin  dry  plates,  as  well  as  their  development, 
so  that  the  operator  must  determine  for  himself  through 
these  time  tests  the  proper  exposures  to  be  given. 

DEVELOPMENT. 

It  is  not  necessary  to  go  over  the  method  of  dry-plate 
development.  Sufficient  is  it  to  caution  against  the  danger 
of  fogging  the  green  and  red  sensitive  plates  by  light  in  the 
darkroom.  It  is  best  to  flow  the  developer  on  these  plates 
in  absolute  darkness,  and  allow  the  development  to  proceed 
for  at  least  a  minute  before  turning  up  the  light  that  is  con- 
sidered safe.  A  record  should  be  taken  of  the  time  required 
in  development. 

REDUCTION  OR  INTENSIFICATION. 

After  perfect  fixing  and  a  good  washing,  should  the  nega- 
tives not  correspond  in  density,  this  can  be  remedied  by 
carefully  intensifying  the  weak  negative  and  reducing  the 
strong  one. 


THREE-COLOR  PROCESSWORK 


131 


Positives  are  made  from  the  three-color  record  negatives, 
on  either  dry  or  wet  plates,  as  the  operator  prefers.  Equally 
good  positives  can  be  produced  by  either  method.  The  posi- 
tives represent  in  their  shadows  just  how  much  ink  of  each 
color  will  be  used  in  the  printing.  One  with  a  well-trained 
eye  for  color  separation  can  determine  by  comparing  them 
with  the  original  copy  whether  they  possess  the  proper  color 
balance  —  that  is,  whether  the  colors  will  be  in  the  propor- 
tion they  are  in  the  copy  when  printed  over  each  other.  The 
proper  color  balance  can  be  restored  by  careful  reduction 
or  intensification  of  the  positives  either  locally  or  over  the 
whole  plates.  The  yellow  plate  is  usually  corrected  by 
painting  on  the  glass  side  of  the  positive  with  a  semitrans- 
parent  color  so  as  to  obstruct  the  light  when  printing 
through  it.  Small  areas  like  lines  may  be  reduced  by  scrap- 
ing the  film  on  the  positive  with  a  sharp  knife. 

THE  HALF-TONE  NEGATIVE. 

The  positives  could  be  placed  in  a  rotary  holder  in  a 
copy  board,  and  turned  to  the  proper  angles  before  making 
the  half-tone  negatives,  or,  better  still,  be  fixed  one  after 
the  other  in  exactly  the  same  position  in  the  positive  holder, 
and  the  half-tone  screen  rotated  as  is  done  in  the  direct 
method. 

ETCHING  THREE-COLOR  BLOCKS. 

There  is  no  difference  in  the  method  of  etching  plates 
for  three-color  and  etching  plates  for  black  printing,  except 
that  it  is  better  to  etch  all  three  plates  together  so  that  the 
color  balance  may  be  preserved.  The  registry  marks  having 
been  preserved  on  the  half-tone  plates,  the  plates  are  turned 
over  to  the  printer  to  prove  them.  If,  after  proving,  it  is 
found  that  one  color  overbalances  the  other  by  being  too 
strong,  the  strong  plate  can  be  given  a  further  etching,  or, 
either  of  the  plates  can  be  reetched  locally  where  necessary. 

SCREEN  ANGLES  FOR  FOUR  COLORS. 

To  avoid  moire,  or  a  pattern,  in  superimposing  screens 
in  four-color  printing  it  is  necessary  to  cross  the  lines  at  the 
most  obtuse  angles  possible.    With  a  cross-line  screen  in 


132 


morgan's  half-tone 


each  printing  this  angle  is,  of  course,  22^  degrees  from  each 
other.  Still  there  is  a  danger  of  pattern  unless  the  stronger 
colors,  blue  and  black,  are  kept  farther  apart.  It  is  found 
better  to  have  30  degrees  between  the  blue  and  black,  and 
15  degrees  between  the  red  and  yellow.  Be  also  careful 
to  put  the  yellow  between  the  red  and  blue.  With  the  circu- 
lar screen  the  following  angles  may  be  chosen:  Black  to 
blue,  30  degrees ;  red  to  yellow,  ijy2  degrees,  yellow  to 
blue,  iyy2  degrees.  The  following  positions  give  the  least 
moire  pattern  and  for  other  visual  reasons  are  the  most 
practical  angles  in  which  to  use  the  four  screens :  yellow, 
75  degrees ;  red,  60  degrees  ;  blue,  90  degrees ;  and  black, 
120  degrees. 

PRINTING  THREE-COLOR  BLOCKS. 

It  is  within  the  power  of  the  printer,  by  skilful  under- 
laying of  the  plate,  to  modify  the  result  in  any  way  he 
pleases,  so  that  corrections  can  be  made  in  many  ways. 
There  should  not  be  any  corrections  for  the  printer  to  make 
after  he  receives  the  final  set  of  proofs  from  the  maker  of 
the  plates.  The  ink  should  correspond  with  the  color  patches 
photographed  with  the  copy  The  best  inks  to  use  are  the 
ones  employed  by  almost  all  three-color  printers.  It  was 
not  intended  to  give  in  these  few  chapters  instructions  in 
presswork  or  the  kind  of  presses  to  use.  Presswork  is  a 
business  entirely  distinct  from  three-color  block  making, 
and  it  is  only  the  latter  the  writer  has  tried  to  the  best  of 
his  ability,  though  briefly,  to  explain. 


OFFSET-PRESS  WORK  IN  NINE  PRINTINGS. 


An  example  of  the  Knapp  Aquatint.    By  courtesy  of  the  Knapp  Company,  Inc„ 
New  York.    Art  publication  branch  of  the  American  Lithographic  Company. 


PHOTOPLANOGRAPHY. 

PRACTICAL 

APPLICATIONS  OF  PHOTOENGRAVING  PROCESSES 
TO  THE  OFFSET  PRESS. 

The  photoengraver  is  most  anxious  to  help  out  the  offset- 
press  printer  if  the  latter  could  but  explain  how  it  could  be 
done ;  but,  as  neither  is  too  well  acquainted  with  the  other's 
method  of  working,  it  is  too  often  a  case  of  the  blind  leading 
the  blind,  when  both  get  away  from  their  proper  course. 

The  photoengraver  makes  plates  for  dry-paper  printing. 
He  cares  little  whether  water  repels  grease  or  vice  versa, 
while  the  offset  pressman  is  a  "  grease-and-water  artist." 
His  work  is  founded  on  the  fact  that  grease  and  water  will 
not  mix.  His  printing-ink  must  have  some  grease  in  it,  and 
the  plate  from  which  he  prints  must  be  dampened  with  a 
roller  wet  with  water  before  it  is  rolled  with  ink.  The  offset 
press  will  occupy  the  field  it  is  intended  for  when  there  is  a 
better  understanding  between  the  photoengraver  and  the 
offset  pressman  as  to  what  are  the  requirements  and  the 
limitations  of  each. 

Photolithography  will  answer  all  the  requirements  of 
the  offset  press  when  it  is  properly  worked,  though  there  are 
few  processworkers  that  know  anything  about  it.  The  meth- 
ods used  in  the  most  successful  photolithographic  establish- 
ment having  been  described  fully,  we  will  now  consider  how 
the  regular  photoengraver  may  apply  to  the  offset  press  some 
of  the  methods  in  every-day  use  in  his  plant. 

GRAINED  ZINC  OR  ALUMINUM  AND  LITHOGRAPHIC  STONE. 

It  might  be  well  first  to  explain  how  it  is  that  grained 
zinc  has  taken  the  place  of  lithographic  stone  as  a  printing 
surface  and  to  correct  the  statement  so  frequently  made  that 
"  zinc  has  exactly  the  same  properties  as  lithographic  stone." 
The  facts  are,  that  owing  to  its  porous  nature  lithographic 
stone  will  absorb  grease  and  water  with  equal  facility,  while 
a  polished  piece  of  zinc  will  absorb  no  more  water  than  a 
piece  of  glass.    Hold  a  piece  of  polished  zinc  under  the  tap 

133 


134 


horgan's  half-tone 


or  allow  it  to  soak  in  water  all  day  and  see  how  the  water  is 
still  repelled  by  it.  Flow  water  over  a  piece  of  ground  glass 
and  it  will  be  found  to  retain  some  moisture,  and  here  we  find 
the  principle  by  which  zinc  has  been  adapted  to  take  the  place 
of  stone.  The  surface  of  a  zinc  plate  can  be  ground  to  hold 
moisture  to  a  greater  degree  than  a  ground  glass  surface, 
owing  to  the  fact  that  when  the  surface  of  zinc  is  scratched 
with  the  proper  cutting  material  its  ductile  surface  is  plowed 
up  into  minute  furrows  crossing  one  another  at  every  con- 
ceivable angle.  These  furrows  or  gutters  in  the  metal  hold 
moisture  by  not  only  capillary  attraction  but  by  what  is  called 
cohesion  or  surface  tension.  And  these  scratches  in  the  zinc 
hold  hardened  grease  in  the  same  manner,  so  that  by  creating 
this  artificial  surface  on  the  zinc  it  mechanically  holds  grease 
and  moisture,  while  lithographic  stone  has  the  same  property 
through  its  natural  power  of  absorption. 

ZINC  FOR  OFFSET -PRESS  WORK. 

Zinc  can  be  grained  by  hand,  but  it  is  a  long,  tedious 
operation  requiring  great  patience  and  much  skill.  The 
thickness  of  the  metal  used  is  from  ten  one-thousandths  to 
forty  one-thousandths  of  an  inch.  Regular  14-gauge  zinc 
used  by  photoengravers  is  eighty-three  one-thousandths  of 
an  inch,  so  that  the  offset  press  zinc  at  its  thickest  is  not 
one-half  as  thick  as  that  used  by  some  engravers.  There  is  a 
still  thinner  zinc  used  to  pull  transfers  on,  called  "  foil "  or 
"  wafer  "  zinc,  so  that  the  difficulties  of  graining  such  thin 
metal  by  hand  can  be  understood.  There  is  a  right  and  a 
wrong  side  to  the  zinc  sheet,  and  the  difference  is  found 
usually  by  laying  the  sheet  in  a  tray  containing  nitric  acid  in 
the  proportion  of  one  ounce  of  acid  to  twenty  ounces  of 
water  and  brushing  the  acid  solution  over  both  surfaces  with 
a  bristle  brush.  The  surface  that  etches  smoothest  is  the 
surface  to  be  grained. 

GRAINING  THE  ZINC  BY  HAND. 

The  sheet  of  zinc  should  be  first  clamped  to  a  block  made 
for  that  purpose  and  the  bends  required  by  the  clamps  should 


PRINTED  ON  OFFSET  PRESS 


COURTESY    NIAGARA  SILK  MILLS 


L1THGRAVURE  BY 
GIES  &  CO.,  BUFFALO 


PRINTED  ON  OFFSET  PRESS 


COURTESY  CHAUTAUQUA  SCHOOL  OF  NURSING  G IEs"'&^CC^^B U FFAL.O 


PHOTOPL  A  NOGRAPH  Y 


135 


correspond  to  the  gripper  bends  on  the  press,  so  that  they 
need  never  to  be  rebent  when  the  zinc  is  regrained.  Instead  of 
grippers  to  hold  the  sheet  secure  to  the  block  while  graining 
it  may  be  tacked  to  the  block  at  the  corners.  The  graining 
materials  are  the  same  as  those  used  in  a  graining-machine, 
and  the  pressure  on  the  graining  material  must  not  be  too 
heavy ;  a  block  of  wood  covered  with  an  iron  plate  being  as 
good  as  any  weight  to  press  the  cutting  sand  on  the  zinc  sur- 
face, while  this  iron-faced  block  is  moved  around  in  small 
circles. 

The  best  advice  that  could  be  given  here  is  to  not  attempt 
to  grain  your  own  plates  by  hand.  Better  purchase  them 
already  grained,  as  photoengravers  do  their  polished  zinc  and 
copper.  Plates  grained  by  machine  are  so  far  superior  to 
those  treated  by  hand  that  should  the  amount  of  work  war- 
rant it  a  graining  machine  is  a  most  essential  addition  to  the 
plant. 

THE  GRAINING  MACHINE. 

A  graining  machine  is  a  water-tight  wooden  box  as  large 
as,  say,  4^4  by  6  feet,  and  about  5  inches  deep.  It  rests  at 
the  corners  on  large  steel  balls  and  is  given  a  vibratory  or 
rotary  motion  by  mechanism  underneath  the  box.  The  plates 
to  be  grained  are  fastened  by  clamps  to  the  bottom  of  the 
box  (as  many  plates  as  will  cover  the  bottom  of  the  box) 
and  covered  with  emery,  pumice  or  sand,  and  sufficient  water 
to  float  the  sand.  Then  the  sand  is  covered  with  marbles 
and  the  machine  started  vibrating  from  150  to  200  revolu- 
tions a  minute,  with  the  result  that  the  marbles,  while  moving 
but  a  short  distance,  press  the  cutting  material  into  the  plate 
and  produce  scratches  in  curves  crossing  each  other  in  all 
directions.  The  time  required  to  grain  a  plate  varies  from 
thirty  to  ninety  minutes,  depending  on  the  cutting  material 
and  the  quality  of  grain  required.  In  some  establishments 
the  sand  is  changed  every  twenty  minutes. 

THE  MARBLES  USED. 

The  balls  used  to  roll  over  the  plate  may  vary  in  size 
from  one-half  inch  to  1  inch  in  diameter  and  can  be  made 


136 


horgan's  half-tone 


of  hardwood,  stone,  glass,  glazed  porcelain,  or  steel.  The 
white  pebbles  found  at  the  seashore  are  also  used.  On  the 
character  of  grain  required  depends  the  kind  of  marbles 
as  well  as  the  scratching  material  used.  When  any  of  the 
marbles  get  flat  on  one  side  they  are  called  "  flat  wheels  " 
and  must  be  thrown  out.  It  requires  as  many  as  5,000 
marbles  of  a  single  kind  to  cover  a  metal  plate  in  a  graining- 
box  of  the  size  mentioned  above.  Glazed  china  and  steel 
marbles  are  the  ones  most  used,  while  wooden  marbles  are 
still  used  for  aluminum  —  a  metal  softer  than  zinc. 
Wooden  marbles  are  also  used  where  the  finest  grain  is 
required  on  zinc,  the  rule  being  that  the  finer  the  grain 
required,  the  lighter  or  smaller  should  be  the  marbles  and 
the  finer  the  scratching  medium ;  while  the  coarser  the  grain, 
the  heavier  or  larger  the  marbles  and  the  coarser  the  sand 
used. 

THE  SCRATCHING  MATERIAL. 

The  grain  given  to  a  metal  surface  may  vary  from  the 
finest  matt  to  the  coarse  and  visible  grain  used  for  poster- 
work.  These  grains  are  given  numbers  which  correspond, 
in  a  measure,  with  the  number  of  the  graining  material  used. 
For  instance,  the  No.  "  000  "  grain  is  produced  with  "  000  " 
emery,  and  so  on  through  "00,"  "  o,"  and  No.  "1,"  which 
is  given  with  No.  "  1  "  sand,  silex,  flint  sand  or  carbo- 
rundum, or  any  material  that  can  be  sifted  through  a  screen 
with  a  mesh  120  to  the  inch.  This  No.  "  1  "  grain  is  called 
a  medium  grain,  suitable  for  the  majority  of  work  both  in 
transferring  and  in  retaining  moisture  on  the  press.  For 
one  of  the  first  things  one  learns  in  offset  printing  is  that 
the  transferrer  prefers  the  finer  grains  while  the  pressman 
has  least  trouble  with  the  coarser  ones;  for  the  reason, 
chiefly,  that  the  transferrer  can  get  solids  easier  on  a  fine 
grain,  while  the  coarser  grains  hold  the  moisture  better  and 
thus  prevent  "  scumming  "  on  the  press. 

The  coarser  grains  are  numbered  2,  3,  4,  5  and  6,  the 
latter  being  used  for  the  coarsest  posterwork. 


PHOTOPLANOGRAPHY 


137 


Above  all  things,  do  not  trust  the  graining  of  the  plates 
to  an  unreliable  person,  remembering  that  the  whole  success 
of  the  work  is  based  on  the  preparation  of  the  plate,  and 
good  work  can  not  be  done  on  an  improperly  grained  plate. 

FURTHER  POINTS  ABOUT  GRAINING. 

Great  care  must  be  used  in  taking  the  grained  plate  out 
of  the  box  to  prevent  scratching  it.  This  may  seem  strange. 
Though  the  surface  of  the  plate  is  covered  with  millions  of 
scratches,  a  single  one  in  a  straight  line  would  spoil  it.  As 
all  of  the  marbles  must  be  removed  and  the  box  cleaned  out 
free  of  scum  before  another  plate  is  grained,  some  of  the 
marbles  can  now  be  taken  out,  the  plate  released  from  the 
clamps  in  the  corners  and  then  drawn  slowly  from  the  box, 
washed  thoroughly  in  running  water,  back  and  front,  taking 
care  not  to  touch  the  face  with  the  fingers,  and  dry  as 
quickly  as  possible.  The  plate  is  then  ready  for  treatment 
by  the  transferrer.  Should  the  grained  plate  be  stored 
away  for  a  long  time  before  use  it  is  well  to  remove  the 
slight  trace  of  oxid  that  may  have  formed,  by  plunging  the 
plate  into  a  bath  of  nitric  acid  —  two  ounces  to  a  gallon  of 
water — for  a  few  minutes  and  then  wash  off  the  loosened 
oxid  under  the  tap  with  a  clean  sponge. 

If  it  is  an  aluminum  plate  use  hydrochloric  acid  instead 
of  nitric. 

To  regrain  a  plate,  first  remove  the  old  transfer  from 
the  plate  with  turpentine,  and  then  get  rid  of  the  turpentine 
with  a  strong  solution  of  potash  and  a  scrubbing-brush. 
After  washing  the  potash  thoroughly  from  the  plate  it  is 
then  put  into  the  graining-box  for  a  fresh  graining. 

PHOTOGRAPHIC  PRINTING  ON  GRAINED  METAL. 

The  photoengraver  will  find  the  following  the  easiest  and 
most  satisfactory  method  of  getting  a  print  in  line  or  half- 
tone on  a  grained  zinc  plate  for  printing  on  the  offset  press. 

He  must  provide  himself  with  powdered  asphalt,  good 
quality  benzol  and  spirits  of  turnpentine.  The  asphalt  need 
not  be  light-sensitive,  and  it  would  be  better  to  wash  it  well 
with  water  to  remove  any  soluble  dirt  and  filter  the  water 


138 


horgan's  half-tone 


from  it.  Then  wash  it  with  alcohol  to  remove  any  material 
in  it  that  may  be  soluble  in  alcohol.  Should  the  asphalt 
discolor  neither  the  water  nor  the  alcohol,  then  it  is  suffi- 
ciently pure  and  does  not  need  that  treatment  afterward. 
Evaporate  the  alcohol  from  it  by  putting  it  on  clean  paper 
in  a  warm  closet  and  then  make  up  a  solution  of : 

Powdered  asphalt   y2  ounce 

Benzol   10  ounces 

Filter  this  asphalt  solution  perfectly.  While  it  is  filter- 
ing fasten  the  sheet  of  thin  grained  zinc  to  a  wooden  block 
by  tacking  it  at  the  corners.  Flow  the  grained  zinc  with  the 
filtered  asphaltum  and  whirl  and  dry  as  usual.  When  the 
asphalt  coating  is  perfectly  dry,  flow  it  with  the  regular 
sensitizing  solution  for  metal  on  hand,  whether  it  be  albu- 
men or  enamel. 

If  it  is  necessary  to  prepare  a  sensitizer  the  following 


will  answer: 

Water    16  ounces 

Albumen,  whites  of  two  fresh  eggs   2  ounces 

Bichromate  of  ammonia  40  grains 


The  albumen  should  be  well  beaten  up  with  an  egg- 
beater  before  being  stirred  into  the  water,  and  ten  drops  of 
water  ammonia,  twenty-six  per  cent,  added  to  the  solution 
after  the  bichromate  of  ammonia  is  dissolved  in  the  albumen 
mixture.    Filter  this  carefully  through  cotton  wool. 

Hold  the  asphalt-coated  grained  zinc  under  the  tap  for 
a  few  moments,  drain  well,  and  flow  with  the  filtered  albu- 
men solution  several  times,  letting  the  first  coating  pass 
away  in  the  sink.  After  flowing  it  from  different  corners, 
at  least  three  times,  place  it  again  in  the  whirler  and  dry 
the  albumen  coating.  Or,  the  zinc  plate  can  be  detached 
from  its  wooden  support,  and  flowed  and  dried  by  laying 
on  a  previously  heated  thick  zinc  or  copper  plate.  The 
things  to  be  avoided  chiefly  are  specks  of  dust  drying  in  the 
albumen  coating ;  heating  the  plate  so  hot  that  it  will  coag- 
ulate the  albumen;  and  the  injurious  effect  of  coal-gas 
heat,  which  has  almost  the  same  effect  on  bichromatized 
glue,  or  albumen,  that  light  has. 


PH0T0PLAN0GRAPHV 


139 


All  the  previous  operations  have,  of  course,  been  carried 
on  in  a  room  lighted  by  yellow  light,  as  well  as  the  present 
one  of  putting  the  metal  plate  in  contact  with  the  negative 
in  a  printing- frame. 

EXPOSURE  TO  LIGHT. 

The  printing- frame  should  have  a  sheet  of  soft,  pure, 
rubber  backing  behind  the  zinc  plate  and  plenty  of  pressure 
to  bring  the  sensitized  surface  of  the  zinc  into  intimate  con- 
tact with  the  film  side  of  the  negative.  A  pneumatic  print- 
ing-frame is  best  for  this  work. 

The  exposure  to  light  must  be  found  by  experiment  and 
should  not  exceed  three  to  four  minutes  of  sunlight,  or 
enclosed  arc  electric  light.  An  actinometer  is  a  valuable 
aid  here  to  determine  the  length  of  exposure. 

After  exposure  the  zinc  plate  is  taken  from  the  printing- 
frame  in  a  darkroom  and  laid  in  a  tray  containing  the  fol- 
lowing dye  bath : 

Water    35  ounces 

Methyl  violet    8  grains 

The  tray  is  rocked  until  the  image  appears  darker  in 
color  than  the  beautiful  golden  yellow  of  the  asphalt 
ground.  It  is  then  washed  with  a  hose  under  the  tap 
quickly  and  flowed  over  with  alcohol  to  completely  coagu- 
late the  albumen.  After  draining  off  the  alcohol  it  is  dried 
in  a  darkroom.  If  the  alcohol  is  diluted  over  one-half  with 
water  it  will  be  found  to  coagulate  the  albumen  more  evenly. 

DEVELOPING  WITH  TURPENTINE. 

When  the  plate  is  thoroughly  dry  it  is  placed  in  a  tray 
containing : 

Spirits  of  turpentine   20  ounces 

Benzin,  good  quality   4  ounces 

The  grained  zinc  will  begin  to  show  almost  immediately 
between  the  lines  and  around  the  dots.  Should  the  white 
dots  in  the  shadows  of  a  half-tone,  for  instance,  not  show 
clearly,  development  may  be  assisted  with  a  tuft  of  cotton 
applied  lightly  to  the  film.  Rocking  the  tray  hastens  the 
development.    Just  as  soon  as  the  image  stands  out  clearly 


140 


morgan's  half-tone 


the  plate  is  once  more  washed  thoroughly  under  the  tap 
until  all  greasiness  disappears,  when  it  is  ready  to  be  desen- 
sitized, rolled  up  and  treated  by  the  offset  pressman,  or 
transferrer. 

TO  SHIP  THE  PLATE  WITHOUT  INJURY. 

To  protect  the  plate  from  injury  during  shipment  all 
that  is  necessary  to  do  is  to  cover  the  image  on  the  zinc 
plate  with  a  light  protective  varnish  of  shellac  laid  on  with 
a  brush.  When  the  plate  reaches  the  offset  pressman  he 
simply  washes  off  the  protective  varnish  with  alcohol,  and 
all  traces  of  alcohol  under  the  tap,  and  the  plate  is  again 
ready  for  use  to  pull  transfers  from  after  the  usual  treat- 
ment with  acified  gum  arabic  solution,  called  the  desen- 
sitizer. 

Where  this  method  of  photographing  on  grained  plates 
is  in  use  it  is  a  good  plan  to  coat  the  grained  plates  with 
asphalt  immediately  after  they  are  grained  and  dried.  This 
prevents  oxidization  of  the  zinc.  It  must  be  remembered 
that  the  asphalt  coating  is  sensitive  to  light  and  can  not  be 
washed  from  the  plate  after  it  is  light-hardened,  so  that 
asphalt-coated  zinc  plates  should  be  kept  in  a  dark  place. 

After  asphalt-covered  plates  are  developed,  exposure 
to  light  is  a  benefit  to  them  as  it  hardens  the  asphalt  image 
further. 

ENAMEL  SOLUTION  ON  GRAINED  PLATES. 

The  enamel  solution  found  in  any  engraving  plant  may 
be  used  on  the  asphalt-coated  grained  zinc  plate  in  the  same 
manner  as  the  albumen  solution  previously  described.  It 
is  exposed  to  light  for  the  same  period  used  in  photorelief 
printing,  and  after  printing  the  enamel  is  rolled  up  with 
transfer  ink  and  developed  as  is  done  in  albumen  printing  on 
polished  zinc. 

Great  care  must  be  taken  that  none  of  the  greasy  ink  is 
rubbed  into  the  grained  zinc,  for  it  can  not  afterward  be 
removed.  In  fact,  this  is  the  great  danger  in  this  enamel 
method.  If  the  plate  is  developed  in  running  water  and  kept 
well  covered  with  clean  water  there  is  little  danger  of  ink 
getting  into  the  grain  when  ordinary  care  is  taken. 


PH0T0PLAN0GRAPHY 


141 


After  development  the  plate  is  washed  well  under  the 
tap,  whirled  to  get  rid  of  the  surface  water  and  dried  quickly. 
It  can  then  be  heated  slightly  to  bring  the  transfer  ink 
together,  and  be  turned  over  to  the  offset  pressman  or  coated 
with  shellac  varnish  for  shipment  away. 

GUMMING  UP  A  GRAINED  ZINC  PLATE. 

The  action  of  gum  arabic  in  repelling  greasy  ink  is  well 
known  to  lithographers,  and  photoengravers  should  at  least 
understand  the  principles  governing  its  use. 

Gum  arabic  or  gum  acacia,  from  the  tree  it  exudes  from, 
is  obtained  best  from  Senegal.  It  contains  an  acid  which 
etches  lithographic  stone  or  zinc  slightly,  so  that  if  a  fresh 
solution  of  gum  arabic  is  brushed  over  a  grained  zinc  plate, 
allowed  to  dry  on  it  and  then  washed  off  with  a  sponge 
and  the  plate  dried  again,  it  could  then  be  put  in  an  offset 
press,  dampened  and  rolled  with  the  dampening  roller  and 
ink,  without  any  danger  that  the  plate  would  take  up  ink 
from  the  roller. 

It  will  be  understood,  then,  in  either  of  the  methods  of 
]  hotoplanography  given  here,  that  after  the  metal  plate  is 
developed,  washed  and  dried,  it  can  be  flowed  with  the 
fresh  gum  arabic  solution,  which  is  allowed  to  dry  on  the 
plate.  The  gum  arabic  can  not  reach  the  plate  where  it  is 
covered  with  asphalt,  while  the  gum  renders  the  zinc  repel- 
lant  to  grease  wherever  it  is  allowed  to  act  upon  the  plate. 

It  has  been  found  advantageous  to  add  other  acids  to  the 
gum  arabic  solution.  The  acids  most  used  are  citric,  gallic, 
tannic,  oxalic  and  phosphoric.  Their  use  on  a  metal  or  stone 
surface  is  called  '  desensitizing." 

DESENSITIZING  SOLUTIONS  FOR   METAL  PLATES. 

The  following  are  the  desensitizing  solutions  most  fre- 
quently used  by  offset-press  transferrers: 

Gum  arabic,  from  Senegal   y2  ounce 

Water,  distilled    8  ounces 

Phosphoric  acid,  in  solution   y2  dram 

The  gum  arabic  should  be  powdered  in  a  mortar  and 
stirred  into  solution  with  a  glass  rod.    The  phosphoric  acid 


142 


horgan's  half-tone 


comes  in  sticks,  also  in  a  fifty  per  cent  solution  and  this  is 
the  better  way  to  buy  it.  There  is  a  syrupy  solution  of 
phosphoric  acid  sold  which  is  an  eighty-five  per  cent  solu- 
tion. It  should  be  diluted  to  make  a  fifty  per  cent  solution, 
as  it  is  more  convenient  to  measure. 

Another  desensitizing  solution  preferred  by  some  trans- 
ferrers is  — 

Water,  distilled    20  ounces 

Gum  arabic,  from  Senegal   1  ounce 

Phosphoric  acid,  solution   y2  dram 

Gallic  acid    ]/2  ounce 

All  desensitizing  solutions  should  be  filtered  before  use 
and  should  be  used  fresh,  as  the  tendency  with  gum  arabic 
solutions  is  to  turn  sour  quickly.  When  it  does  get  sour 
a  little  powdered  chalk  is  used  to  sweeten  it,  though  a  little 
carbolic  acid,  oil  of  cloves  or  cinnamon,  or  gum  camphor 
is  used  in  the  desensitizers  sold  ready  for  use,  to  prevent 
fermentation  in  them. 

SPONGES  MUST  BE  CLEAN. 

Everything  used  while  working  on  a  grained  zinc  for 
the  offset  press  must  be  clean.  Clean  water  and  absolutely 
clean  sponges  are  necessary.  The  sponge  used  for  one  pur- 
pose should  not  be  used  for  any  other,  and  there  should  be 
a  plentiful  supply  of  clean  water  at  hand. 

Aluminum  plates  on  the  offset  press  have  a  tendency  to 
get  lighter  while  printing  from  them ;  zinc  plates  on  the 
press  have  a  tendency  to  get  heavier,  or  thicken,  so  that  the 
gumming-up  on  a  zinc  plate  must  be  properly  done.  There 
is  a  tendency  for  the  grease  in  the  printing-ink  to  repel 
water  from  the  edges  of  every  line  and  dot  on  the  plate,  and 
after  driving  away  the  water  encroach  itself  on  the  water 
areas.  This  information  gives  the  photoengraver  warning 
to  make  transfers  or  prints  on  zinc  as  sharp  as  possible  and 
lighter  than  heavier  in  thickness  of  lines  or  dots. 

USEFUL  INFORMATION  REGARDING  PHOTOPLANOGRAPHY. 

Photolithographic  transfers  for  the  offset  press  should 


HIGH-LIGHT  HALF-TONE. 

Copyright  by  Harper  &  Bros.,  from  a  drawing  by  Vernon  Howe  Bailey. 
The  Walker  Engraving  Company,  New  York. 


PII0T0PLAN0CRAPHY 


143 


be  reversed  as  regards  right  and  left.  That  is,  they  should 
read  backward. 

Photographic  prints  direct  on  the  grained  zinc  for  use  on 
the  offset  press  should  read  to  the  right. 

Photolithographic  transfers  for  planographic  printing 
direct  from  the  metal  should  read  to  the  right. 

Photographic  prints  direct  on  the  metal  for  planographic 
printing  direct,  and  not  by  offset,  should  be  reversed. 

The  best  transfers  for  planographic  printing  can  be  made 
from  photointaglio  engraved  plates. 

Grained  zinc  plates  will  oxidize,  and  so  will  grained 
aluminum  plates,  if  they  are  not  kept  away  from  moisture. 

Do  not  scrape  out  the  grain  on  a  metal  plate  to  remove 
dirt  or  make  corrections. 

Half-tone  negatives  for  planographic  printing  should  be 
made  by  a  high-light  half-tone  method. 

HIGH-LIGHT  HALF-TONE  NEGATIVES. 

For  the  offset  press  and  frequently  for  relief  plates  a 
high-light  half-tone  negative  is  wanted.  That  is  a  negative 
in  which  the  highest  light  dots  in  the  copy  are  filled  up. 
Such  negatives  are  usually  made  in  a  camera  specially  fitted 
with  a  frame  holding  the  screen  which  can  either  be  with- 
drawn entirely  from  the  camera  or  the  frame  holding  the 
screen  can  be  swung  inside  the  camera  out  of  the  way. 
When  making  high-light  negatives  in  such  a  camera  the 
exposure  is  made  through  the  half-tone  screen  as  usual,  and 
then  the  screen  is  removed  and  an  exposure  of  one-sixth 
to  one-tenth  the  time  given  to  the  copy  without  the  screen. 
No  flash  exposure  is  used.  On  development  the  high  lights 
should  fill  up  so  that  with  proper  intensification  they  will 
not  print  either  on  photolithographic  transfer  paper  or  on 
metal. 

Another  and  simpler  method  is  this :  After  the  regular 
exposure  is  made,  move  the  half-tone  screen  as  far  from  the 
sensitive  plate  as  possible  and  make  another  exposure  with 
the  high-light  stop  for,  say,  ten  seconds,  or  enough  to  fill  up 
the  highest  lights  on  intensification. 


144 


horgan's  half-tone 


The  writer  made  high-light  half-tones  as  early  as  1879  by 
putting  an  ordinary  negative  and  a  half-tone  screen  together 
and  getting  a  half-tone  positive  from  the  combination.  It  is 
now  called  the  Sears  process,  and  some  firms  are  paying  a 
royalty  for  the  use  of  it. 

GUM  SOLUTION  FOR  ROLLING  UP  ZINC. 

Before  pulling  offset  transfers  and  sometimes  after  a 
very  slight  first  bite,  if  the  image  is  delicate,  some  operators 
roll  up  the  zinc  with  a  soft  transfer  ink  after  "  gumming 
up  "  the  plate,  as  it  is  called.  The  gum  solution  they  use 
is  the  following : 

Water  15  parts 

Saturated  solution  of  gum  arabic  10  parts 

Phosphoric  acid    1  part 

Gallic  acid    5  parts 

This  solution  is  spread  over  the  zinc  with  a  flat  camel's- 
hair  brush  and  allowed  to  remain  a  half  minute  or  more 
before  being  wiped  off  with  a  clean  and  damp  sponge.  The 
ink  for  rolling  up  should  contain  a  little  middle  linseed  oil 
varnish. 

THE  VANDYKE  PROCESS. 

This  process  was  patented  in  the  United  States  in  1880 
and  was  known  as  Hagotype.  The  principle  of  the  process 
is  that  weak  hydrochloric  acid  will  soften  bichromatized 
albumen  or  gelatin  that  has  been  hardened  by  the  action  of 
light.  It  is  utilized  in  this  way :  After  an  inked  image  has 
been  developed  on  a  zinc  plate  by  the  ordinary  bichromatized 
albumen  method,  it  has  under  the  ink  an  image  in  hardened 
albumen.  The  plate  is  dried  and  rolled  up  with  a  thin  but 
perfect  coating  of  good  quality  etching-ink,  warmed  slightly 
so  that  the  ink  will  attach  itself  intimately  to  the  bared 
zinc.  The  plate  is  then  laid  in  a  weak  hydrochloric  acid 
bath  for  a  few  minutes,  or  until  the  acid  has  had  time  to 
soak  through  the  ink  coating  and  attack  the  albumen  image 
under  the  ink.  The  plate  is  then  developed  by  gently  rub- 
bing with  cotton  wool,  when  a  reversed  image  will  appear 
on  the  zinc  which  can  be  resined  and  etched. 


ROTARY  PHOTOGRAVURE. 
The  Rotary  Photogravure  Co.,  Passaic,  N.  J. 


ROTARY  PHOTOGRAVURE. 


THE  NEW 

PHOTOMECHANICAL  METHOD  WHICH  GIVES  MOST 
ARTISTIC  RESULTS  ON  INEXPENSIVE  PAPER. 


The  latest  and  most  valuable  application  of  photography 
to  the  printing-press,  so  far  as  artistic  results  go,  is  the 
engraving  of  photogravure  on  a  cylinder  so  that  a  web  of 
paper  can  be  printed  from  it  at  high  speed.  It  is  the  ideal 
method  for  illustrated  periodicals.  Germany  led  in  its  use 
for  this  purpose,  though  an  illustration  from  a  photogra- 
vure on  a  cylinder  was  shown  in  an  Austrian  magazine  in 
1897.  In  the  Process  Year  Book  for  that  year,  page  125, 
Mr.  William  Gamble  describes  the  method. 

Potters  have  for  generations  cleaned  with  a  knife  blade 
the  ink  from  intaglio  plates  from  which  they  print  the 
designs  for  transference  to  pottery.  Wall-paper  and  fabric 
printers  who  use  intaglio  engraved  rolls  to  print  from  have 
for  many  years  used  what  they  call  a  "  doctor,"  which  is 
a  sharp  steel  blade,  to  clean  off  the  surplus  ink  from  the 
roll.  Marinoni,  the  famous  pressbuilder  of  Paris,  built  a 
rotary  photogravure  press  in  the  eighties  in  which  the  wip- 
ing of  the  plate  was  done  by  means  of  a  doctor  as  in  wall- 
paper printing. 

The  engraving  of  the  roll  by  photography  was  not  per- 
fected then  and  it  remained  for  Karl  Klic,  to  whom  we  owe 
so  much  in  photogravure,  to  perfect  the  method  of  engra- 
ving rolls  for  rotary  photogravure  printing.  As  usual  he 
kept  his  methods  secret.  Many  fine  art  reproductions  were 
produced  in  colors  in  England  toward  the  close  of  the  last 
century  as  the  result  of  Klic's  skill,  the  Rembrandt  Intaglio 
Printing  Company's  photogravures,  made  in  that  way,  being 
highly  prized  by  art  lovers  everywhere. 

The  publication  in  The  Inland  Printer  of  December, 
1908,  of  a  photogravure  in  colors,  a  realistic  reproduction 
of  a  portrait  in  oils,  made  the  whole  printing  world  realize 
that  an  improved  method  of  reproducing  colors  in  printing- 

10  145 


146 


horgan's  half-tone 


ink  had  arrived  in  the  United  States.  To  Mr.  Charles  W. 
Saalsburg's  perseverance  must  be  credited  that  accomplish- 
ment. 

ROTARY  AND  FLAT  PRINTED  PHOTOGRAVURE. 

The  essential  difference  between  rotary  and  ordinary 
photogravure,  printed  from  flat  plates,  is  this:  The  photo- 
gravure on  the  cylinder  must  be  engraved  in  such  a  manner 
that  the  deepest  shadows  will  have  continuous  bearings  for 
the  metal  wiper  or  doctor,  or,  in  other  words,  that  the  ink- 
holding  cavities  on  the  cylinder  be  in  the  form  of  cells  sur- 
rounded by  thin  walls  of  the  metal  cylinder.  This  will  be 
explained  later.  The  most  successful  way  of  accomplishing 
this  was  worked  by  Klic  and  an  Austrian  named  Klisch, 
and  has  been  in  use  by  the  Rembrandt  Intaglio  Printing 
Company  in  England  since  the  late  nineties. 

Another  method  is  to  etch  on  the  cylinder  a  half-tone 
intaglio,  instead  of  in  relief,  taking  care  that  at  least  single 
lines  of  the  metal  cylinder  remain  even  in  the  deepest 
shadows  to  act  as  bearers  for  the  metal  wiper,  or  doctor. 
By  examining  with  a  microscope  the  screen  lines  in  a  photo- 
gravure print  the  two  methods  may  be  distinguished. 

THE  KLIC  AND  KLISCH  SCREENS  ON  THE  CYLINDER. 

These  pioneers  of  rotary  photogravure  found  it  best  to 
separate  the  etched  areas  of  the  cylinder  with  fine  lines, 
leaving  the  cells  for  holding  the  ink  of  the  same  dimensions 
but  of  different  depths.  To  make  their  method  more  easily 
understood  we  will  take  a  screen  of  transparent  thin  lines 
ruled  on  glass  at  angles  of  forty-five  degrees  to  its  sides 
and  crossing  each  other  so  as  to  leave  opaque  squares 
instead  of  transparent  squares,  as  in  an  ordinary  half-tone 
screen.  Now  if  a  print  is  made  from  this  screen  on  a  piece 
of  photogravure  carbon  tissue  and  it  is  squeegeed  in  con- 
tact with  a  copper  cylinder,  then  developed  and  etched  with 
chlorid  of  iron  until  the  protected  lines  of  the  screen 
threaten  to  be  eaten  away,  it  will  be  found  when  printing 
from  such  a  cylinder  on  a  rotary  photogravure  machine, 


ROTARY  PHOTOGRAVURE 


147 


with  a  doctor  for  wiping  away  the  surplus  ink,  that  the 
resulting-  print  will  be  in  rich,  velvety  tones,  the  lines  of  the 
screen  being  completely  obliterated. 

The  screen  lines  are  intact  on  the  roll,  with  square  cells 
between  them.  These  cells  are  left  quite  full  of  ink  when 
the  doctor  passes  over  them,  while  the  screen  lines,  level 
with  the  surface  of  the  cylinder,  are  wiped  clean  of  ink  by 
the  doctor.  The  elasticity  of  the  impression  on  soft  paper 
causes  the  pyramids  of  ink,  after  leaving  their  cells  on  the 
cylinder  for  the  paper,  to  run  together  and  give  the  effect  of 
a  solid,  rich,  velvety  depth  of  color  which  can  not  be 
obtained  by  any  other  machine-printing  method,  and  it  is 
this  rich,  velvety  color  that  gives  the  strength  and  value  to 
photogravure. 

Should  these  same  cell  walls  or  partitions  be  cleaned  with 
a  rag,  as  in  hand-printed  photogravure,  much  of  the  ink 
would  be  wiped  out  of  the  ink  cells  unavoidably.  Further, 
when  using  a  metal  wiper  instead  of  a  rag  a  much  thinner 
ink  can  be  used. 

The  screen  lines  on  the  cylinder,  besides  producing  the 
necessary  cell  walls,  act  as  bearers  for  the  doctor  and  pre- 
vent the  roll  from  wearing  as  soon  as  would  be  expected 
with  long  editions.  In  fact,  they  are  what  make  rotary 
photogravure  printing  possible. 

PHOTOGRAVURE  ON  A  CYLINDER. 

The  ordinary  photogravure-worker,  or  those  who  have 
studied  the  chapter  on  photogravure  in  this  book  and  who 
fully  appreciate  the  necessity  of  screen  lines  on  the  cylinder 
for  rotary  photogravure,  will  require  to  know  the  further 
steps  to  engrave  photogravure  on  a  cylinder. 

The  cylinders  can  be  solid  copper  rolls;  or  better,  hol- 
low copper  cylinders  slightly  tapered  on  the  inside  so  that 
they  can  be  forced  on  a  mandrel.  Some  of  the  latest  cylin- 
ders are  steel  tubes  on  which  a  shell  of  copper  has  been 
deposited  by  electrolysis.  These  rolls  are  turned  absolutely 
true  in  a  lathe  and  polished  there,  the  polishing  of  a  cylin- 


148 


horgan's  half-tone 


der  being  even  a  more  mechanical  operation  than  polishing 
a  flat  plate. 

WAYS  FOR  GETTING  THE  SCREEN  LINES  IN  THE  RESIST. 

The  pitch  of  the  screen  employed  is  generally  150  to  175 
lines  to  the  inch.  Should  the  negative  be  made  in  the  camera, 
the  screen  can  be  inserted  in  front  of  the  sensitive  plate 
and  in  contact  with  it  if  the  latter  is  a  dry  plate.  A  short 
exposure  to  a  sheet  of  white  paper  covers  over  the  negative 
with  a  network  of  screen  lines  of  equal  thickness  through- 
out and  does  not  interfere  in  the  slightest  with  securing  all 
the  gradations  of  the  copy  in  the  negative. 

A  second  method  of  impressing  the  carbon  tissue  with 
screen  lines  is  done  either  before  or  after  making  the  print 
from  the  ordinary  positive  on  the  tissue.  This  requires  a 
second  print  on  the  carbon  tissue  from  the  half-tone  screen 
for  sufficient  time  to  print  the  lines  on  it.  This  method  is 
the  common  practice. 

A  third  method,  preferred  because  it  prevents  the  possi- 
bility of  "devils"  in  the  metal,  is  the  following:  Two 
sheets  of  carbon  tissue  are  printed,  one  from  the  transparent 
line  screen  which  is  transferred  to  the  cylinder  first  and 
developed  there;  then  a  carbon  print  from  the  positive 
which  is  transferred  on  top  of  the  screen  already  on  the 
cylinder  and  also  developed.  When  both  films  dry  down, 
the  relief  made  does  not  interfere  with  etching.  As  Mr. 
Huson  has  found  that  "  devils  "  are  caused  by  minute  pin- 
holes in  the  gelatin  tissue,  which  permit  chlorid  of  iron  to 
go  through  and  etch  those  pits  called  "  devils  "  in  the  cop- 
per, this  double  tissue  on  the  cylinder  prevents  this  annoy- 
ance for  the  reason  that  pinholes  in  one  of  the  tissues  are 
covered  up  by  the  other. 

PREPARING  THE  CYLINDER  AND  TRANSFERRING. 

The  metal  cylinder,  like  a  copper  plate,  must  be  carefully 
prepared  to  insure  the  gelatin  adhering  to  it  during  the  etch- 
ing. This  is  a  most  important  matter.  If  the  surface  of  the 
cylinder  could  be  grained,  the  resist  would  stick;  but  this 


ROTARY  PHOTOGRAVURE 


149 


is  impossible,  as  it  would  leave  a  tint  in  printing.  The 
cylinder  must  keep  its  polish  and  yet  the  gelatin  must  adhere 
to  it.   One  way  to  accomplish  this  is  as  follows : 

After  the  roll  is  treated  with  clean  potash  solution  to 
remove  the  grease,  it  is  washed  and  gone  over  with  one  dram 
of  sulphuric  acid  in  ten  ounces  of  water.  This  removes 
the  stain  caused  by  the  potash  and  gives  the  copper  a  slight 
tooth.  When  the  acid  solution  is  washed  from  the  roll  thor- 
oughly the  metal  is  dried  quickly  and  painted  over  with  the 
following  substratum,  which  makes  the  tissue  adhere  during 
etching: 

Two  hundred  grains  of  a  hard  gelatin,  like  Coignet's 
"  Gold  Seal,"  is  dissolved  in  ten  ounces  of  water;  ten  grains 
of  chrome  alum  are  dissolved  in  one  ounce  of  water.  Both 
solutions  are  heated  slightly,  and  while  the  gelatin  is  being 
stirred  briskly  the  chrome  alum  solution  is  poured  slowly 
into  the  gelatin.  While  the  clean,  dry  and  warm  copper 
roll  is  turned,  it  is  given,  with  a  flat  brush,  a  thin  coating 
of  this  substratum,  after  which  it  is  allowed  to  dry  in  a  place 
free  from  dust. 

TRANSFERRING  AND  DEVELOPING  THE  TISSUE. 

Information  regarding  the  preparation  of  the  positive 
and  printing  the  carbon  tissue  will  be  found  in  the  chapter 
on  photogravure  as  the  operations  are  similar,  the  only 
difference  being  that  the  printed  gelatin  resist  must  be  trans- 
ferred later  to  a  cylinder  instead  of  a  flat  surface. 

The  copper  cylinder  can  be  arranged  to  turn  in  a  trough 
of  cold  water  in  which  the  printed  carbon  tissue  is  put  to 
soak.  Care  must  be  taken  to  remove  air-bells  from  its  front 
and  back  surfaces.  When  the  tissue  begins  to  flatten,  it  is 
quickly  adjusted  to  the  position  indicated  by  pencil-marks 
which  have  been  drawn  on  the  cylinder.  All  the  water  pos- 
sible is  pressed  out,  the  cylinder  raised  from  the  trough, 
the  tissue  squeegeed  securely  to  the  cylinder,  and  all  surplus 
moisture  wiped  from  the  back  with  soft  cloths.  The  roll 
is  allowed  to  "  set  "  for  at  least  ten  minutes  while  the  trough 
is  being  prepared  with  water  of  about  no°  F. 


150  h  organ's  half-tone 

As  copper  absorbs  and  holds  heat,  it  is  well,  if  the  roll  is 
a  solid  one,  to  allow  only  its  surface  to  dip  in  the  warm 
water  when  developing.  The  roll  is  steadily  turned  over 
the  developing  trough  until  the  paper  backing  is  loosened, 
when  it  is  stripped  off  and  the  development  continued. 
Local  development  can  be  given  to  the  tissue  by  pouring 
the  warm  water  from  a  pitcher  or  from  a  vessel  with  a  small 
spout  when  small  areas  in  the  tissue  are  to  be  treated.  When 
the  image  shows  proper  development,  the  tissue  is  treated 
with  alcohol  and  water,  gradually  increasing  the  alcohol 
until  pure  alcohol  is  used  to  drive  out  all  the  water  possible 
from  the  film,  when  the  roll  can  be  revolved  rapidly  and 
dried.  It  is  now  ready  for  covering  the  margins  with 
asphalt  varnish. 

ETCHING  THE  COPPER  ROLL. 

The  method  of  etching  a  cylinder  is  similar  to  that  of 
etching  a  flat  plate,  except  that  the  cylinder  must  be  rotated 
in  a  trough  containing  the  etching  solution.  In  practice, 
fewer  changes  in  the  strength  of  the  mordant  is  found  nec- 
essary. For  some  subjects  a  chlorid  of  iron  bath  of  32 ° 
Baume  will  be  found  to  work  satisfactorily. 

The  important  point  to  be  observed  in  cylinder  etching  is 
that  the  screen  lines  are  not  etched  away,  for  it  must  be 
again  recalled  that  on  the  preservation  of  these  lines  as  par- 
titions between  the  ink  cavities  and  as  bearers  for  the  metal 
wiper  the  whole  success  of  rotary  photogravure  printing 
depends. 

After  cleaning  the  asphalt  protection  from  the  roller  with 
turpentine  and  benzin  and  removing  the  gelatin  resist  with 
potash  the  photogravure  roll  is  ready  for  the  press. 

OTHER  METHODS  OF  ROTARY  PHOTOGRAVURE. 

Dr.  Eduard  Mertens  showed  on  Easter  Sunday,  1910, 
in  a  supplement  to  the  Freiburger  Zeitung,  of  Freiburg, 
Germany,  excellent  photogravures  printed  on  ordinary  news- 
print paper.  Since  then  several  papers  have  used  his  method 
with  success.    Dr.  Mertens  engraved  a  half-tone  intaglio, 


ROTARY  PHOTOGRAVURE 


151 


as  the  writer  was  doing  in  New  York  in  1894,  except  that 
Dr.  Mertens  etched  his  intaglio  half-tone  on  a  cylinder  with 
the  advantage  that  the  metal  wiper  leaves  the  intaglio  cavi- 
ties fuller  of  ink  than  the  rag  wiper  does  on  a  flat  plate.  His 
method  differs  from  Klic,  Klisch  and  Sallburg,  from  the 
fact  that,  instead  of  using  a  carbon  tissue  for  the  resist  on 
the  metal,  Mertens  coats  the  entire  cylinder  with  bichroma- 
tized  gelatin  and  prints  from  a  positive  half-tone  direct  on 
the  cylinder. 

DR.  EDUARD  MERTENS*  METHOD. 

To  coat  the  cylinder  with  the  bichromatized  glue,  Dr. 
Mertens  uses  a  simple  apparatus  whereby  the  glue  solution 
is  flowed  on  the  cylinder  in  a  spiral. 

The  bottle  containing  the  sensitized  glue  is  on  an  ele- 
vated stand  from  which  the  solution  flows  through  a  glass 
cock  and  rubber  tube  to  a  bent  and  pointed  glass  tube,  from 
which  it  flows  in  a  spiral  stream  on  the  cylinder,  which  is 
mechanically  revolved  in  a  lathe  and  at  the  same  time 
moved  laterally.  The  convolutions  of  the  spiral  stream  of 
glue  immediately  merge  into  each  other  and  form  a  con- 
tinuous coating  of  the  sensitive  material.  The  rate  of  coat- 
ing is  about  \  x/2  inches  a  minute.  The  drying  of  the  coating 
is  assisted  with  an  air-blast. 

THE  MERTENS  NEGATIVE  AND  POSITIVE. 

Dr.  Mertens  first  makes  a  continuous  tone  negative,  from 
which  he  makes  a  half-tone  copy  through  a  slit  diaphragm, 
which  gives  him  a  positive  largely  in  lines  running  in  one 
direction,  particularly  in  the  deep  shadows.  These  lines 
are  at  an  angle  of  forty-five  degrees  to  the  axis  of  the  cylin- 
der, so  as  not  to  interfere  with  the  movement  of  the  doctor 
when  wiping  the  cylinder  later.  The  positive  has  pure 
whites  in  the  highest  lights  and  a  full  range  of  gradation 
from  black  to  white.  This  positive  is  coated  with  rubber 
and  collodion,  and  stripped  from  its  glass  support  and  used 
as  a  pellicle  on  the  cylinder  by  drawing  it  in  contact  with 
the  cylinder  with  another  transparent  film  over  this  pellicle. 


152 


horgan's  half-tone 


It  can  also  be  secured  to  the  sensitized  roll  with  castor  oil, 
as  is  done  in  photographic  printing  on  stone. 

MERTENS'  METHOD  OF  PRINTING  ON  THE  CYLINDER. 

To  get  a  photographic  print  on  the  sensitized  cylinder, 
it  is  exposed  to  eight  mercury  vapor  lamps  the  full  length 
of  the  cylinder.  These  lamps  are  enclosed  in  light-tight 
boxes  and  in  a  semicircle,  so  that  light  can  fall  only  on  the 
cylinder  perpendicularly.  As  the  lamps  will  not  work  unless 
raised  at  one  end,  the  cylinder  must  also  be  placed  at  the 
same  angle  as  the  lamps  while  it  is  slowly  revolved.  The 
exposure  lasts  from  eight  to  fifteen  minutes  to  lights  with  an 
aggregate  intensity  of  about  four  thousand  candle-power. 

After  printing  and  development  the  glue  film  may  be 
"  burned  in  "  to  form  an  enamel  acid  resist,  as  in  ordinary 
half-tone  etching.  The  etching  of  the  roll  then  becomes  a 
simple  operation,  quite  similar  to  that  of  ordinary  half-tone 
and  permitting  reetching  to  vary  the  effects. 

TRANSFERRING  AN  ENAMEL  RESIST  TO  THE  ROLL. 

A.  Villain  suggested  in  the  Process  Photogram  for  July 
and  August,  1898,  a  method  of  attaching  a  film  of  resist 
to  metal  plates  or  rollers.  His  idea  worked  out  in  the  fol- 
lowing manner  would  give  a  perfectly  practical  process  for 
engraving  rolls  for  fabric  and  wall-paper  printing: 

If  the  reader  will  make  up  an  enamel  solution  as  given 
in  the  chapter  on  half-tone  and  will  apply  this  enamel  to 
paper  as  told  in  the  instructions  for  coating  paper  for 
photolithography  in  this  book,  he  can  then  print  on  this 
paper  from  a  positive  that  is  reversed,  as  regards  right  and 
left,  and  develop  the  paper  under  the  tap  as  enamel  is  devel- 
oped on  metal.  Having  the  copper  roll  perfectly  clean,  as 
recommended  in  the  chapter  on  the  Rembrandt  method,  the 
paper  containing  the  developed  gelatin  enamel  print  is 
squeegeed  in  position  on  the  roll  and  allowed  to  dry  per- 
fectly. 

When  the  paper-coated  film  on  the  roll  is  absolutely  dry, 
the  roll  is  turned  slowly  over  a  single  or  double  piped  gas 


ROTARY  PHOTOGRAVURE 


153 


stove  with  sufficient  flame  to  burn  off  the  paper  the  whole 
length  of  the  roll.  The  charred  paper  can  be  removed  with 
a  brush  and  the  burning-in  of  the  enamel  proceeded  with  as 
explained  in  the  chapter  on  half-tone  enamel. 

Before  etching  and  after  the  roll  is  properly  protected 
with  asphalt,  the  carbonized  enamel  on  the  roll  should  be 
brushed  vigorously  with  a  mixture  of  one  ounce  of  hydro- 
chloric acid  in  ten  ounces  of  water  to  which  three  ounces 
of  common  salt  has  been  added.  It  will  then  be  seen  if  the 
design  on  the  roll  requires  retouching  or  any  parts  need 
scraping  away  before  etching.  The  etching  can  be  done 
with  a  single  bath  of  chlorid  of  iron  at  about  32 °  Baume. 
The  enamel  roll  is  cleaned  with  strong  potash,  washed  and 
dried. 

UTILIZING  A  DAGUERROTYPE  IMAGE  ON  A  ROLL. 

The  idea  of  etching  a  daguerrotype  plate  so  that  it  could 
be  printed  from,  which  was  tried  out  so  thoroughly  after  the 
daguerrotype  was  given  to  the  world  in  1839,  has  at  last 
been  solved  in  New  York  by  Mr.  Carleton  and  others  asso- 
ciated with  him.  It  is  utilized  chiefly  for  engraving  copper 
rolls  either  in  relief  or  intaglio  for  printing  on  fabrics  or 
paper,  so  that  if  rotary  photogravure  printing  does  not 
become  popular  it  will  not  be  because  the  methods  of  apply- 
ing photography  to  engraving  the  rolls  are  limited. 


TRANSFERRING  ENAMEL  TO  A  ROLL. 


A  novel  enamel  method  suggested  by  J.  M.  Hascher  is 
applicable  to  copper  rolls  as  well  as  flat  plates.  It  also  pos- 
sesses the  advantage  of  dispensing  with  a  reversed  negative. 
His  enamel  is  composed  of : 


The  gelatin  is  swelled  and  dissolved  in  700  parts  of  water 
and  the  bichromate  in  300  parts  of  water.    Both  solutions 


Coignet's  superfine  gelatin 

Water   

Bichromate  of  potash. . . . 

Liquid  ammonia   

Pure  glycerin  


100  parts 
1,000  parts 


30  parts 
10  parts 
60  parts 


154 


horgan's  half-tone 


are  heated  to  86°  F.,  and  the  bichromate  slowly  poured  into 
the  gelatin  solution ;  filter  once  and  add  the  ammonia  and 
glycerin  and  keep  at  1040  F.  in  a  dish.  Float  well-glazed 
paper  on  this  and  dry  in  the  dark.  The  dry  paper  is  printed 
under  a  half-tone  negative  until  the  image  is  plainly  visible 
in  brown.  The  copper  plate,  having  been  cleaned  with  alco- 
hol and  chalk,  is  taken  into  the  darkroom,  and  the  paper 
containing  the  half-tone  print  and  the  copper  are  placed 
in  a  dish  of  cold  water  at  the  same  time.  When  the  paper 
becomes  flaccid  it  is  floated  on  the  copper  and  squeegeed 
to  it.  After  blotting  off  the  water  the  plate  is  allowed  to 
stand  for  a  quarter  of  an  hour  until  the  swelling  of  the 
gelatin  fixes  the  film  firmly  to  the  plate.  The  copper  plate 
is  then  turned  face  down  on  hot  water  of  105 0  F.  until  the 
paper  loosens,  when  it  is  carefully  removed.  The  light- 
hardened  gelatin  adhering  to  the  copper  is  then  washed 
gently  under  the  tap,  dried,  and  the  gelatin  burned  in  as  in 
the  enamel  process. 


ORDINARY  CROSS-LINE  SCREEN.  ROTARY  PHOTOGRAVURE  SCREEN. 


EVERY  PROCESS  PHOTOGRAPHER 

SHOULD  BE 

FAMILIAR  WITH  THE  FOLLOWING  FACTS  AND 
FORMULAS. 


MUTILATION  OF  COPY  BY  ENGRAVERS. 

In  one  of  the  early  numbers  of  The  Inland  Printer  was 
an  editorial  crying  out  against  the  mutilation  of  copy  by 
engravers.  One  of  the  paragraphs  was  as  follows :  "  No 
one  who  has  much  to  do  with  ordering  processwork  can 
have  failed  to  remark  the  general  disregard  which  engravers 
seem  to  have  respecting  the  condition  in  which  the  original 
copy  is  returned  to  the  customer.  This  fault  is  not  the  fault 
alone  of  cheap  houses.  It  is  prevalent  among  the  best  engra- 
vers, and  it  is  as  unnecessary  as  it  is  annoying." 

This  editorial  was  copied  into  various  trade  papers  and 
did  much  to  stop  the  evil.  There  is  still  opportunity  for 
improvement  in  this  matter.  There  are  still  firms  who  per- 
mit their  men  to  hammer  a  valuable  drawing  full  of  ten- 
ounce  carpet  tacks  to  secure  it  to  the  copy  board.  There 
is  no  excuse  for  this.  There  are  several  inventions  now 
for  securing  copy  to  the  plan  board  by  the  use  of  clips  of 
various  kinds  and  sizes.  If  a  tack  must  be  used  there  are 
glass-headed  push-pins  that  will  not  mutilate  copy  to  the 
extent  of  a  nail  or  tack.  Any  engraver  who  can  not  devise 
means  of  securing  copy  to  a  board  without  driving  spikes 
through  it  had  better  go  out  of  business  at  once,  for  he 
will  eventually  drive  away  all  his  trade  anyhow. 


NUMBERING  DIAPHRAGMS. 

Every  diaphragm  possesses  a  focal  value  which  is  the 
relation  of  its  diameter  to  the  equivalent  focal  length  of 
the  lens  to  which  it  belongs,  and  it  should  be  numbered 
accordingly.  To  find  this  number  divide  the  equivalent 
focus  of  the  lens  by  the  diameter  of  the  circular  aperture 
in  the  diaphragm.    For  example:   The  focal  length  of  the 

155 


156 


horgan's  half-tone 


lens  is  12  inches  and  the  diameter  of  the  diaphragm  is  j£ 
inch,  then  12  -f-  =  24.  The  number  of  the  diaphragm 
is  therefore  24  and  is  marked  thus,  f/24.  This  system  is 
a  most  convenient  one,  as  it  assists  in  the  calculation  of 
exposures.  The  exposure  varies  as  the  square  of  the  area 
of  the  stop.  For  instance:  If  f/8  stop  requires  y2  min- 
ute exposure,  under  the  same  conditions  f/11  would  require 
1  minute  exposure;  f/16,  2  minutes;  f/22,  4  minutes; 
f/32,  8;  f/45,  16;  f/64,  32;  f/90,  64  minutes;  each 
smaller  stop  requiring  twice  the  exposure  of  the  preceding 
one. 


EQUIVALENT  FOCUS  OF  A  LENS. 

The  equivalent  focus  of  a  process  lens  is  the  focus  of 
parallel  rays  entering  the  lens.  It  is  usually  found  by  focus- 
ing the  lens  on  an  object  over  150  feet  away  and  then  meas- 
uring the  distance  between  the  diaphragm  and  the  ground 
glass.  This  is  the  equivalent  focus.  Another  way  is  to 
focus  any  piece  of  copy  exactly  same  size,  then  measure 
the  distance  exactly  between  the  copy  and  the  inner  surface 
of  the  ground  glass.  One-quarter  this  distance  will  be  the 
equivalent  focus  of  the  lens. 


SUBSTITUTE  FOR  GROUND  GLASS. 

The  best  substitute  for  a  broken  ground  glass  is  another 
ground  glass  and  it  is  very  easily  made.  Take  a  few  cents' 
worth  of  finely  powdered  emery,  dust  it  over  a  sheet  of  flat 
plain  glass,  wet  it  with  water,  and  then,  with  a  flat  iron  or 
another  piece  of  glass,  rub  the  emery  with  a  circular  motion 
over  the  glass.  It  does  not  take  long  to  make  a  new  ground 
glass  in  this  way. 

A  varnish  which,  flowed  on  plain  glass,  gives  very  much 
the  effect  of  ground  glass  is  made  by  mixing  two  ounces  of 
ether,  one  ounce  of  benzol  and  one-fourth  ounce  of  alcohol. 
In  this  dissolve  powdered  sandarac  or  dammar  in  the  pro- 
portion of  from  ten  to  twenty-five  grains  to  the  ounce.  It 
dries  quickly  and  without  heat. 


FACTS  AND  FORMULAS 


157 


PHOTOGRAPHING  SILVERWARE. 

It  is  well  known  that  polished  silver  surfaces  reflect 
light  in  such  a  way  as  to  make  it  impossible  to  photograph 
them  properly.  One  way  to  overcome  the  mirror-like  sur- 
face is,  if  the  silver  is  a  vessel  that  will  hold  water,  to  fill 
it  with  ice-water  just  before  photographing.  This  causes 
moisture  from  the  air  to  be  condensed  on  the  silver  surface 
and  prevents  reflections.  A  second  method  is  to  dab  the  silver 
over  with  fresh  putty.  This  deposits  on  the  silver  a  film 
of  oil  and  whiting  which  also  destroys  reflections.  The 
third  way  is  to  heat  on  an  iron  plate  some  muriate  of 
ammonia  (sal  ammoniac).  When  the  salt  burns  it  gives  off 
a  smoke  which  deposits  a  white  oxid  on  the  silver  surface 
that  is  held  in  the  fumes.  This  oxid  deposit  can  be  wiped 
off  without  injury  to  the  silver  surface. 


GLASS  CLEANING. 

When  the  negative  films  on  glass  are  old  there  is  no  bet- 
ter solution  to  soften  them  up  than  a  mixture  of  bichromate 
of  potash,  sulphuric  acid  and  water.  It  can  be  made  as 
follows :  To  every  gallon  of  water  add  sixteen  ounces  of 
sulphuric  acid  and  two  pounds  of  bichromate  of  potash. 
This  solution  can  be  used  for  a  long  time.  The  old  nega- 
tives are  laid  in  with  separators  —  small  pieces  of  lead  — 
between  them.  The  films  should  be  softened  in  twelve  hours. 
The  films  are  scraped  off  and  saved  with  the  silver  waste, 
and  then  the  glass  is  given  a  good  scrubbing  with  a  stiff 
brush  and  plenty  of  clean  water.  The  edges  of  the  glass 
should  not  be  neglected. 


ALBUMEN  SUBSTRATUM. 

In  building  a  structure  of  any  kind  it  is  most  important 
that  the  foundation  be  right,  so  in  wet-plate  negative-making 
it  is  necessary  that  the  substratum  on  which  the  negative 
is  built  up  be  perfect,  and  there  is  none  that  can  compare 
with  the  old  reliable  albumen  made  up  in  the  following  way : 


158 


morgan's  half-tone 


One  ounce  of  fresh  egg  albumen  is  beaten  to  a  froth, 
mixed  in  forty  ounces  of  water,  and  one  dram  of  water 
ammonia  added.  The  whole  is  well  filtered  and  flowed  only 
on  one  side  of  thoroughly  cleaned  glass. 


WHY  OLD  COLLODION  GIVES  SHARPER  NEGATIVES. 

Photoengravers  find  that  new  collodion  gives  a  fuzzier 
negative  than  old  collodion;  while  the  latter,  though  slow, 
makes  a  sharp,  crisp  negative.  The  reason  for  it  is  probably 
this :  The  old  collodion  being  a  dark  amber  color  acts  as  a 
color  screen  and  prevents  halation  in  the  negative.  To 
prove  this,  remove  the  amber  color  from  the  old  collodion 
by  the  addition  of  a  few  grains  of  carbonate  of  soda,  which 
destroys  the  amber  color  but  prevents  the  collodion  from 
producing  as  sharp  a  negative. 


INCREASING  EXPOSURE. 

Exposure  must  be  increased  as  the  square  of  the  area 
of  aperture  in  the  stop  decreases.  Exposure  also  increases 
in  proportion  to  the  square  of  the  camera  extension.  The 
absorption  of  light  by  a  mirror  used  in  reversing  negatives 
increases  rapidly  as  the  mirror  becomes  tarnished.  The  use 
of  a  prism  usually  doubles  the  exposure  and  the  period  of 
exposure  increases  with  the  size  of  the  prism. 


COLLODION  EMULSION  OR  DRY  PLATES  FOR 
COLORWORK. 

As  to  whether  dry  plates  purchased  from  a  reliable 
maker,  or  collodion  emulsion,  also  from  a  reliable  source, 
is  the  more  economical  and  satisfactory,  is  a  question  in 
which  there  is  no  agreement  among  practical  men.  Some 
color-plate  makers  use  collodion  emulsion  exclusively,  while 
others  producing  equally  good  work  prefer  dry  plates.  In 
either  case  the  supply  house  either  furnishes  a  demon- 
strator to  show  how  their  goods  are  best  used  or  they  supply 


FACTS  AND  FORMULAS 


159 


full  printed  working  instructions.  Dry  plates  have  the 
advantage  of  being  always  ready,  can  be  used  anywhere 
and  developed  at  any  time,  while  they  usually  give  cleaner 
negatives.  Collodion  emulsion,  on  the  other  hand,  can  be 
handled  much  like  a  wet  plate  and  almost  any  character 
of  a  negative  can  be  had  from  it  by  intensification  and  after- 
treatment.  The  drawback  to  collodion  emulsion  was  that 
it  was  rarely  free  from  dirt  specks.  This  trouble  has  been 
overcome  in  some  of  the  newer  emulsions. 


PRESERVATIVE  FOR  DEVELOPED  PLATES. 

There  are  occasions  when  an  operator  wants  to  expose 
and  develop  all  the  wet  plates  he  can  and  leave  the  intensi- 
fication until  later.  The  writer  was  the  only  out-of-door 
photographer  connected  with  a  daily  paper  in  the  world 
during  the  years  1876-79.  He  carried  with  him  collodion, 
silver  bath,  and  developer.  When  photographing  paintings 
in  an  art  exhibition  or  documents  in  a  public  library,  he 
only  developed  the  plates  and  flowed  them  with :  Water, 
three  to  four  ounces ;  glycerin,  one  ounce,  and  acetic  acid, 
one-fourth  ounce.  This  solution  was  flowed  over  the  well 
washed  and  drained  developed  plate,  and  it  was  put  in  a 
grooved  plate  box  and  fixed  and  intensified  at  night. 


BLACK  SPECKS  ON  NEGATIVES. 

Whenever  black  specks  appear  on  a  negative  after  devel- 
opment it  is  usually  due  to  some  form  of  sulphur  in  the 
bath.  It  usually  comes  when  hard  rubber  trays  or  holders 
are  used  for  the  bath.  If  you  employ  a  glass  bathholder 
you  will  be  safe  except  from  the  rubber  dipper  used  to  raise 
and  lower  the  glass  to  and  from  the  bath.  Sulphur  is  used 
to  vulcanize  the  hard  rubber,  and  if  the  latter  is  not  kept 
varnished  it  will  give  those  black  specks.  All  hard  rubber 
utensils  should  be  thoroughly  cleaned  in  strong  soda  solu- 
tion, dried  thoroughly,  and  lacquered  with  a  thin  shellac 
varnish  to  which  sufficient  lampblack  is  added  to  make  it 
a  good  black. 


160 


horgan's  half-tone 


RESTORING  AN  "  OVERCUT  "  NEGATIVE. 

It  will  often  happen  that  an  operator  has  "  overcut "  a 
negative  in  one  spot  and  does  not  want  to  throw  the  nega- 
tive away.  Let  him  take  a  little  of  the  iron  developer  and 
add  to  it  a  few  drops  of  the  silver  solution  from  the  bath, 
just  enough  to  turn  it  slightly  brownish.  Now  with  a  drop- 
ping tube  drop  this  iron-silver  solution  carefully  on  the  spot 
to  be  strengthened.  It  had  better  be  done  in  the  darkroom 
to  avoid  fog  and  carefully  watched  so  as  to  not  overinten- 
sify.  When  the  spot  is  considered  sufficiently  strengthened, 
wash  the  negative  and  blacken  in  the  usual  way. 


LEAD  INTENSIFIED 

One  ounce  of  nitrate  of  lead  and  one  and  one-half 
ounces  of  ferricyanid  of  potassium  are  dissolved  in  sixteen 
ounces  of  hot  water,  which  gives  a  saturated  solution ;  two 
and  one-half  ounces  of  acetic  acid  is  then  added.  After 
fixing,  the  negative  is  cleared  with  one  ounce  of  nitric  (or 
hydrochloric)  acid  in  twenty  ounces  of  water.  The  lead 
intensifier  is  used  in  a  porcelain  tray  and  the  negative  laid 
in  it.  After  a  few  minutes'  rocking,  the  negative  is  bleached 
white.  It  is  then  well  washed  under  the  tap  and  flowed  with 
one  ounce  of  either  sulphid  of  sodium  or  ammonium  in 
twenty  ounces  of  water.  Should  the  negative  show  any 
tendency  to  stain,  the  acid  solution  previously  mentioned 
will  clear  it  up. 


GRAY  BORDERS  FROM  BLACK  DRAWINGS. 

If  solid  black  borders  on  white  paper  are  photographed 
through  a  screen  until  the  white  paper  high-light  dots  are 
closed  up  entirely,  and  then  the  whole  drawing  covered 
up  with  a  sheet  of  white  blotter  so  as  to  give  a  flash  expo- 
sure long  enough  to  make  small  dots  over  the  blacks,  a 
half-tone  negative  is  had  of  the  black  border  in  half-tone 
dots  surrounded  by  high  lights,  representing  the  white  back- 
ground, so  closed  up  that  they  will  not  print  on  metal. 


FACTS  AND  FORMULAS 


161 


FOG  AND  ITS  CAUSES. 

What  is  termed  "  fog  "  in  wet-plate  photography  is  an 
obscuration  over  a  portion  or  all  of  the  negative  after  devel- 
opment. It  may  arise  from  the  silver  bath,  from  the  col- 
lodion, or  from  diffused  light  in  the  plateholder,  the  camera 
box,  or  the  darkroom. 

A  new  silver  bath  will  cause  a  fog  over  the  whole  plate 
if  it  is  alkaline  or  is  not  iodized  sufficiently.  A  few  drops 
of  c.  p.  nitric  acid  will  cure  the  alkalinity,  and  leaving  a 
collodion  plate  in  the  bath  until  it  absorbs  sufficient  iodin 
will  cure  the  other  fog.  An  old  collodion  will  frequently 
work  with  a  new  bath  when  new  collodion  will  give  fog. 
The  bath  or  developer  being  too  hot  will  bring  about  fog, 
and  so  will  fumes  from  sewer  gas,  coal  gas  or  from  a  kero- 
sene stove.  Fumes  of  ammonia  and  hydrosulphuret  of 
ammonia  are  sure  causes  of  fog.  Diffused  light  in  the 
camera  may  come  from  a  small  hole  in  the  front  board  of 
the  camera  box,  or  from  reflected  light  entering  the  lens, 
or  from  too  much  light  in  the  darkroom,  or  stray  light  get- 
ting in  through  a  hole  or  crack  in  the  partitions.  These  are 
causes  of  fog  over  the  whole  plate. 

Fog  coming  from  stray  light,  called  light  fog,  is  in  the 
film ;  while  fog  that  comes  from  the  bath  itself  or  devel- 
oper, called  chemical  fog,  usually  lies  on  the  surface  of  the 
film  and  can  be  removed  with  a  piece  of  wet  cotton. 

When  fog  is  produced  by  light  leaking  into  the  camera 
box  or  plateholder  it  shows  itself  in  streaks  over  the  plate, 
and  these  point  to  where  the  light  comes  from,  so  the  trouble 
may  be  remedied. 

Impure  nitrate  of  silver  and  old  white  crystals  of  sul- 
phate of  iron  will  cause  fog,  and  so  will  an  insufficiency  of 
acetic  or  other  acid  in  the  developer,  so  that  eternal  vigi- 
lance is  the  price  of  freedom  from  fog,  though  skilled  oper- 
ators never  experience  this  trouble. 


11 


162 


horgan's  half-tone 


TO  PURIFY  A  SILVER  BATH. 

For  a  played-out  silver  bath  of  one  gallon  procure  a 
three-gallon  porcelain  evaporating  dish,  pour  into  it  half 
a  gallon  of  water  and  into  this  water  pour  the  old  silver 
bath.  It  will  make  a  yellow  solution,  caused  by  the  iodids 
that  are  set  free.  These  can  be  filtered  out.  Then  put 
the  bath  in  the  evaporating  dish  over  heat  and  boil  down 
until  it  becomes  a  yellow,  pasty  mass.  Continue  the  heat 
until  it  gives  off  brown  fumes.  Shut  off  the  heat  from 
under  the  dish,  and  while  the  residue  is  cooling  keep  stir- 
ring it  until  it  breaks  up  into  particles  like  brown  sugar. 
Dissolve  this  sugar-like  salt  in  the  amount  of  distilled  water 
you  require  to  make  the  bath  up  to  the  proper  bulk.  Put 
it  in  the  sun,  in  a  clear  glass  bottle,  for  a  few  days  until  it 
is  clear.  Filter,  strengthen  with  nitrate  of  silver  up  to  45 °, 
test  for  alkalinity  with  litmus  paper.  If  it  is  not  acid,  add 
c.  p.  nitric  acid  until  litmus  paper  in  it  just  turns  red  and 
you  have  a  perfect  silver  bath. 


PINHOLES  IN  NEGATIVES. 

The  appearance  of  small  transparent  spots  in  the  nega- 
tive after  development  is  one  of  the  troubles  of  the  wet- 
plate  photographer  and  it  is  likely  to  come  from  the  follow- 
ing causes :  Dust  on  the  glass  is  a  most  prolific  cause,  and 
this  dust  may  be  induced  by  brushing  the  surface  of  the 
glass  briskly  during  cold  weather  with  a  fine-haired  dust 
brush.  This  electrifies  the  glass  and  causes  any  dust  in  the 
air  to  adhere.  Of  course,  dust  in  the  collodion  will  also 
produce  pinholes  and  these  can  be  eliminated  by  filtering 
the  collodion.  When  the  bath  is  new,  pinholes  can  be 
caused  by  insufficient  iodid  in  the  bath ;  and  when  the  bath 
is  old,  because  of  too  much  iodid  in  the  bath  solution.  The 
first  condition  is  cured  by  allowing  a  plate  coated  with  col- 
lodion to  remain  a  long  time  in  the  bath,  and  when  the  bath 
is  overcharged  with  iodids  the  best  remedy  is  to  evaporate 
it  down  to  dryness,  as  told  elsewhere. 


FACTS  AND  FORMULAS 


163 


DRY  PLATES  IN  PROCESSWORK. 

Dry  plates  are  coming  more  and  more  into  use  in  process- 
work.  The  makers  of  each  brand  of  plates  furnish  such 
complete  instructions  for  their  use  that  it  is  unnecessary  to 
give  any  directions  here.  Where  copy  can  be  had  only  in 
a  public  library,  or  private  building,  or  can  not  be  brought 
to  the  processworker's  studio,  then  dry  plates  must  be  used. 
Panchromatic  and  tri-color  plates  can  be  used  for  the  color 
separation,  where  the  copy  is  in  colors ;  and  contrast  dry 
plates,  with  glycin  or  pure  hydrochinon  development,  when 
the  copy  is  in  line  or  a  half-tone  negative  is  required.  All 
photoengravers  should  be  acquainted  with  contrast  dry 
plates  and  their  development.  One  thing  that  should  be 
said  is,  that  where  a  photographer's  time  is  constantly 
employed  at  process  negative-making  the  wet-plate  process 
is  far  more  economical,  besides  giving  more  suitable  nega- 
tives. Where  a  process  negative  is  required  only  occasion- 
ally, then  the  dry-plate  method  may  be  used. 


SUBSTITUTES  FOR  IODID  OF  POTASSIUM. 

To  dissolve  the  metal  iodin  in  water,  iodid  of  potassium 
is  commonly  used,  but  as  the  latter  is  a  most  expensive 
chemical  the  following  substitutes  have  been  suggested: 
Dissolve  the  iodin  to  saturation  in  denatured  alcohol  and 
then  add  this  alcoholic  solution  to  water  to  make,  with 
cyanid,  the  cutting  solution  or  to  iodize  the  plate  in  intensifi- 
cation. 

Or,  use  caustic  potash  as  follows : 

Iodin  75  grains 

Caustic  potash  35  grains 

Water  10  ounces 

Dissolve  the  caustic  in  two  ounces  of  the  water  and  then 
dissolve  the  iodin  in  this  strong  caustic  solution.  After 
which  add  the  rest  of  the  water  and  then  nitric  acid  drop  by 
drop  until  the  solution  turns  a  rich  wine  color.  Should  too 
much  acid  be  added  a  precipitate  is  thrown  down,  which 
more  caustic  will  take  up.   This  solution  does  not  keep  well. 


164 


horgan's  half-tone 


DARKROOM  VENTILATION,  HEAT  AND  DUST. 

To  ventilate  the  darkroom  and  keep  out  the  summer  dust 
is  largely  a  question  of  construction.  There  is  much  econ- 
omy in  having  the  darkroom  cool,  clean  and  well  ventilated. 
Besides  sparing  the  health  of  the  operators  it  saves  many 
a  make-over,  which  is  not  only  a  great  waste  of  chemicals 
but  what  is  more  costly  —  the  waste  of  a  valuable  operator's 
time. 

Ventilators  should  be  at  both  floor  and  ceiling,  trapped 
for  light  and  covered  with  muslin  on  a  frame  that  can  be 
removed  and  brushed  clean  daily.  As  most  darkrooms  are 
located  where  the  heat  is  most  uncomfortable  in  summer, 
negatives  will  be  found  to  fog.  The  cure  for  this  is  to  keep 
the  chemicals  cool.  Ice  can  be  used  in  the  darkroom  to 
great  advantage.  The  collodion  especially  should  be  cool, 
then  the  bath,  and  lastly  the  developer.  Each  operator  can 
judge  for  himself  how  best  to  utilize  ice  for  that  purpose, 
and  a  few  pounds  of  ice  properly  used  will  be  paid  for  in 
the  better  and  greater  quantity  of  work  that  can  be  turned 
out.  A  proper  temperature  in  winter  is  just  as  essential 
in  the  darkroom. 


SCHLIPPE'S  SALT  INTENSIFIED 

After  bleaching  the  negative  with  either  copper  solution 
or  iodin  and  washing  well  it  can  be  turned  into  a  beautiful 
scarlet  color,  which  is  strongly  nonactinic,  by  flowing  it  with 
five  to  ten  grains  of  Schlippe's  salt  to  each  ounce  of  water. 
Schlippe's  salt  is  sodium  sulphantimoniate  and  is  obtained 
by  dissolving  sulphid  of  antimony  in  sodium  hydrate  and 
adding  sulphur.  Should  this  scarlet  negative  not  be  dense 
enough  it  can  be  treated  with  copper  and  silver,  which  gives 
a  most  intense  black. 


ZING  AND  COPPER  ETCHERS 

HAVE  PAID 

MUCH  MONEY  FOR  THESE  FORMULAS  AND  METHODS. 


ALBUMEN  SENSITIZER  WITH  GLUE. 


The  writer  has  found  the  addition  of  a  little  glue  to  the 
albumen  formula  used  in  sensitizing  zinc  makes  the  exposed 
print  develop  quicker,  which  is  important  on  a  newspaper. 
He  used : 


Enough  water  ammonia  is  added  to  this  solution,  drop 
by  drop,  to  turn  it  a  straw  color. 


As  the  purified  Syrian  asphalt  can  now  be  purchased  in  a 
powdered  form,  those  who  wish  to  try  this  oldest  and  most 
perfect  of  the  photoetching  processes,  and  have  plenty  of 
time  to  give  the  exposure  to  sunlight,  will  find  the  following 
to  be  a  simple  way  to  proceed  successfully :  Dissolve  one 
ounce  of  the  purified  Syrian  asphalt,  or  bitumen  of  Judea,  as 
it  is  sometimes  called,  in  about  twelve  to  fifteen  ounces  of 
pure  anhydrous  benzol.  Filter  through  cotton  several  times 
into  an  amber  bottle,  as  the  solution  is  affected  by  light.  To 
prevent  it  being  too  brittle  it  is  necessary  to  add  a  little  oil, 
say  one  dram  of  oil  of  lavender  and  also  one-eighth  ounce 
of  Venice  turpentine.  In  a  dark  room,  flow  this  over  a 
metal  plate  and  whirl  to  get  an  even  coating.  It  dries  so 
quickly  that  it  is  better  to  secure  the  plate  in  the  whirler, 
polished  side  up,  and  then  pour  some  of  the  asphalt  solution 
in  the  center  and  whirl.  Evaporate  the  benzol  out  thor- 
oughly and  then  print  for,  say,  thirty  minutes  in  sunlight 
to  several  hours  on  a  cloudy  day.  Develop  the  plate  in  tur- 
pentine and  wash  the  turpentine  from  the  plate  with  a  strong 
stream  of  water.   It  is  ready  to  etch  at  once. 


Water  

Albumen  of  two  fresh  eggs 

Le  Page's  glue  

Ammonium  bichromate  .  . . 


,25  ounces 
2  ounces 
Yz  ounce 
45  grains 


ASPHALT  PROCESS. 


165 


166 


horgan's  half-tone 


THE  DRY  ENAMEL  PROCESS. 

The  following  process  is  still  being  sold  as  a  secret.  It 
is  prized  highly  by  those  who  have  the  patience  to  handle 
it  properly.  As  the  coating  is  a  hygroscopic  one,  changing 
in  character  with  the  amount  of  moisture  in  the  atmosphere, 
it  is  not  entirely  practicable  in  places  where  the  climate  is 
subject  to  sudden  changes  as  is  the  case  in  coast  cities.  In 


its  simplest  form  it  is  as  follows : 

Water  10  ounces 

Albumen  (whites  of  two  fresh  eggs)   2  ounces 

White  rock  candy,  or  white  sugar  y2  ounce 

Bichromate  of  ammonia  %  ounce 

Chromic  acid  75  grains 

Aqua  ammonia   %  ounce 


When  this  solution  is  mixed  and  filtered  it  is  flowed  on 
the  copper  plate  as  the  regular  enamel,  dried  and  printed 
under  a  negative  as  usual.  Instead  of  developing  with  water 
it  is  taken  into  a  dampened  room  and  brushed  over  with 
finely  powdered  anhydrous  carbonate  of  soda  until  the 
image  stands  out  clear.  One  can  get  all  kinds  of  effects  by 
breathing  on  the  plate.  If  powder  should  stick  to  any  por- 
tion of  the  plate  where  it  is  not  wanted,  a  little  finely  pow- 
dered salt  will  remove  it.  Now  burn  in  the  enamel  as  usual 
and  develop  with  cold  water,  rubbing  away  the  powder  with 
a  wet  sponge.  To  remove  scum  from  the  plate  try  a  little 
damp  salt  or  a  very  weak  potash  solution.  Carbonate  of 
magnesia  may  be  used  in  place  of  the  soda  for  development. 
Dextrin  may  be  used  in  place  of  the  rock  candy  or  sugar, 
in  fact  every  operator  using  the  process  has  his  own  secret 
formula. 


SCUM  ON  ENAMEL  PRINTS. 

So  prevalent  is  the  appearance  of  scum  after  the  devel- 
opment of  an  enamel  that  most  etchers  use  a  clearing  solu- 
tion, before  submitting  the  developed  print  to  the  chlorid 
of  iron,  either  in  the  tub  or  the  etching  machine.  The  prin- 
cipal causes  for  scum  might  be  enumerated  briefly  as  follows : 


etchers'  formulas  167 

Imperfect  cleaning  of  the  metal ;  portions  of  a  previous 
print  being  left  on  the  copper ;  the  negative  not  being  suffi- 
ciently intense,  particularly  in  the  shadow  dots ;  the  enamel 
being  too  thick ;  enamel  solution  too  new  or  too  old ;  bad 
bichromate,  or  the  solution  too  acid ;  too  long  a  time  between 
coating  the  plate  and  using  it ;  too  long  a  time  between 
printing  and  developing  it ;  overheating  the  plate  when 
drying,  particularly  when  it  has  albumen  in  it ;  drying  over 
a  poor  gas  stove  when  the  fumes  injure  the  enamel;  fog- 
ging the  plate  by  exposing  it,  at  some  time  after  sensitizing 
and  before  development,  to  too  much  light;  lack  of  con- 
tact in  printing;  too  much  heat  from  the  arc  lights  when 
printing;  too  much  exposure;  underdevelopment  when  in 
too  much  of  a  hurry;  insufficient  washing  both  before  and 
after  staining  the  plate  with  a  dye  ;  bad  quality  dye. 


ZINC  RUINED  BY  OVERHEATING. 

Zinc  is  peculiarly  affected  by  temperatures,  and  roughly 
stated  the  changes  are  about  as  follows:  Zinc  when  cold 
or  at  normal  temperature  is  somewhat  brittle,  but  heated 
above  the  boiling  point  of  water  —  2120  F.  to  3000  F. — 
it  is  quite  ductile  and  malleable,  and  it  is  at  the  latter  tem- 
perature it  should  be  rolled.  In  the  rolling  some  sheets  may 
be  allowed  to  get  hotter  than  they  should  and  thus  lose 
their  ductility.  At  between  3000  F.  and  4000  F.  zinc 
becomes  brittle,  and  it  should  never  be  heated  above  4000  F. 
when  burning  in  the  enamel  upon  it,  for  above  4000  F.  the 
character  of  the  metal  changes  entirely.  It  becomes  brittle, 
and  remains  so  on  cooling.  Copper  is  heated  to  7000  F. 
when  burning  in  the  enamel  upon  it,  and  as  some  zinc  melts 
at  that  temperature  it  can  be  understood  that  enamel  can 
never  be  carbonized  on  zinc  as  it  is  upon  copper.  Zinc 
should  never  be  heated  above  4000  F.,  for  the  change  that 
takes  place  at  that  temperature  not  only  destroys  the  cohe- 
siveness  of  the  metal  but  tends  to  loosen  the  enamel  coating 
from  the  zinc. 


168 


HORGAN  S  HALF-TONE 


COLD-ENAMEL  PROCESS  FOR  ZINC 

What  has  been  termed  a  cold-enamel  process  suitable  for 
zinc,  where  there  is  danger  of  destroying  the  zinc  by  heat, 
is  as  follows :  The  prepared  zinc  is  covered  with  a  thin 
and  even  coating  of  carefully  filtered  asphalt  solution  in 
turpentine.  When  this  asphalt  is  dry,  wash  the  greasy  sur- 
face from  it  with  either  a  little  alcohol  or  ammonia  in  water. 
When  water  flows  on  it  readily,  sensitize  the  plate  with 
either  enamel  or  bichromatized  albumen ;  print  and  develop 
as  usual.  When  the  developed  print  is  dry,  develop  with 
turpentine,  which  will  remove  the  asphalt  from  the  portions 
you  wish  to  etch,  the  enamel  coating  protecting  the  asphalt 
in  the  light-hardened  parts.  In  this  way  is  gotten  an 
asphalt  resist  on  metal  in  a  few  minutes  exposure.  Shellac 
or  dragon's-blood  varnish  can  be  used  in  place  of  asphalt, 
and  alcohol  instead  of  turpentine  used  to  develop  it  after 
the  colloid  is  developed. 


ANOTHER  COLD-ENAMEL  PROCESS. 

An  excellent  cold-enamel  process  for  zinc  can  be  had  by 
flowing  the  zinc  first  with  a  thin  and  even  film  of  dragon's- 
blood,  or  shellac,  dyed  red,  in  alcohol ;  then  flowing  with  a 
bichromatized  enamel.  The  enamel  is  printed,  developed  and 
dried,  and  then  the  plate  is  immersed  in  alcohol  for  about 
ten  seconds,  when  it  is  taken  out  and  washed  under  the  tap. 
The  alcohol  softens  the  dragon's-blood  or  shellac  and  the 
quick  dash  of  water  washes  off  the  alcohol  and  dislodges 
the  softened  varnish  from  the  metal  before  the  water  has 
had  time  to  soak  through  the  light-hardened  glue.  The 
plate  can  now  be  further  developed  with  a  tuft  of  cotton, 
and  with  the  aid  of  the  water  from  the  tap  all  the  alcoholic 
varnish  that  was  softened  by  the  alcohol  can  be  removed. 
If  some  of  the  light-hardened  enamel  comes  away  it  does 
not  make  any  difference,  because  the  dragon's-blood  or  shel- 
lac image  on  the  metal  is  the  best  possible  acid  resist,  with 
the  further  advantage  that  it  is  in  intimate  contact  with  the 
metal. 


etchers'  formulas 


169 


THE  DRAGON'S-BLOOD  POWDER-BOX. 

The  writer  described  in  The  Inland  Printer  a  form  of 
container  for  the  dragon's-blood  powder  that  is  being  gen- 
erally adopted.  In  nearly  all  plants  the  powder  is  kept  in 
a  high  box,  with  an  open  front.  Into  this  front  is  brushed 
the  surplus  powder  from  the  plate.  Now  if  this  box  was 
made  dust-tight,  with  a  door  in  front  that  would  slide  up 
and  down  like  a  window  sash,  no  dust  could  get  out  when 
the  box  is  not  in  use.  If  the  back  of  the  box  is  of  muslin, 
drawn  taut  on  a  frame,  and  an  electric  fan  is  placed  back 
of  this  muslin  enclosed  in  an  air  duct  opening  to  the  outer 
air,  you  have  a  powder-box  that  will  not  allow  any  powder 
to  escape  into  the  workroom.  The  proper  way  of  using 
such  a  box  is  this :  The  raising  of  the  front  door  should 
start  the  fan  going,  which  draws  the  air  into  the  box  and 
through  the  muslin  at  the  back  of  the  box.  The  powder 
is  filtered  from  the  air  by  the  muslin  and  deposits  on  the 
surface  of  the  muslin,  from  which  it  can  be  brushed  occa- 
sionally. A  tinsmith  will  make  an  air  duct  to  enclose  the 
portion  of  the  back  of  the  box  covered  with  muslin,  and 
make  the  duct  funnel-shaped  so  that  it  just  encloses  »the 
fan  and  then  continues  out  of  the  window.  Each  engraver 
can  use  his  ingenuity  to  fit  this  idea  to  his  own  situation. 


THE  AUSTRIAN  ETCHING  PROCESS. 

The  plate  is  sensitized  with  asphalt,  printed,  developed 
with  turpentine,  washed  and  given  a  good  first  bite.  It  is 
then  gummed  and  rolled  up  with  a  thin  ink  diluted  with  oil 
of  spike.  The  plate  is  heated  until  the  oily  ink  melts  and 
runs  down  the  sides  of  the  line,  forming  a  big  shoulder. 
The  plate  is  powdered  with  finely  ground  asphalt.  Asphalt 
that  sticks  to  the  bottom  of  the  plate  between  the  lines  is 
scraped  away.  Then  the  plate  is  etched  until  the  shoulder 
is  eaten  away.  The  plate  is  again  rolled  up  with  soft  ink, 
heated  until  the  ink  runs  down  as  before,  then  powdered 
with  asphalt  and  proceeded  with  as  before  until  three  bites 


170 


horgan's  half-tone 


are  given.  After  which  the  plate  is  cleaned  of  all  acid  pro- 
tection, inked  up  again  and  powdered,  and  an  effort  made 
to  get  rid  of  the  shoulders.  The  method  requires  hours, 
which  is  considered  no  drawback  to  the  process  in  Austria. 


STRENGTH  OF  ETCHING-BATHS  FOR  ZINC. 

The  question  of  the  strength  of  the  etching-bath  for  zinc 
depends  on  the  strength  of  the  acid,  the  quality  of  the  zinc, 
the  character  of  the  image  to  be  etched,  the  strength  of  the 
acid  resist,  the  temperature,  and  whether  the  etching  is  to 
be  performed  in  a  tub  or  a  machine.  The  makers  of 
machines  supply  instructions  for  the  acid  solutions  to  be 
used  in  their  machines,  so  we  will  only  consider  the  tub  here. 

The  nitric  acid  is  usually  purchased  at  40 °  Baume  in 
strength,  and  it  should  be  tested  to  see  that  it  is  that  strength. 
The  first  bath  can  be  anywhere  from  one  ounce  of  nitric 
acid  to  from  twenty  to  eighty  ounces  of  water.  Both  solu- 
tions will  etch  ordinary  "  hard  "  zinc ;  it  is  only  a  question 
of  time,  the  weak  bath  requiring  so  much  longer  time. 
Experienced  etchers,  on  a  newspaper  for  instance,  will  use 
a  first  bath  of  one  ounce  of  acid  to  ten  ounces  of  water  on 
strong  work. 

With  the  second  etching  it  is  all  a  question  once  more 
of  the  character  of  the  work  and  the  depth  of  the  first  bite. 
It  is  customary  to  add  only  about  double  the  quantity  of 
acid  used  the  first  time.  The  period  of  the  second  bite  may 
be  not  longer  than  the  first  one. 

For  the  third  bite  the  quantity  of  the  acid  added  can  be 
double  the  amount  already  in  the  bath,  and  the  etching 
period  can  also  be  double  that  of  the  second  bite.  For  the 
fourth  bite  more  acid  can  be  added  than  was  added  for  the 
third  bite,  and  the  period  of  etching  also  increased.  The 
period  of  any  bite  ends  when  the  finest  dots  or  lines  in  the 
plate  show  a  tendency  to  be  undercut. 

Successful  etching  can  be  learned  only  by  experience. 


FACTS  FOR  FOREMEN  AND  FINISHERS 

AND  FOR 

WORKMEN  AND  APPRENTICES  AT  PROCESSWORK  OF 
ANY  KIND. 

COINS  FOR  WEIGHTS. 
Should  a  process  man  be  without  weights  he  can  use 
United  States  coins  to  weigh  chemicals  and  the  weights  will 


be  found  approximately  as  follows : 

A  silver  dollar  and  nickel  will  weigh  about   I  ounce 

Half-dollar  and  a  dime  will  weigh  about   y2  ounce 

Half-dollar  will  weigh  about  200  grains 

A  dime  and  a  nickel  will  weigh  about   x/\  ounce 

A  nickel  will  weigh  about   Ye  ounce 

A  cent  will  weigh  about   50  grains 

A  dime  will  weigh  about  ¥l2  ounce 


POINTS  ABOUT  WEIGHTS  AND  MEASURES. 
An  ounce  of  metallic  silver  contains  480  grains,  while 
an  ounce  of  nitrate  of  silver  weighs  only  437^  grains.  Metal- 
lic silver  is  sold  by  troy  weight,  while  nitrate  of  silver  is  sold 
by  avoirdupois  weight.  All  solid  chemicals  are  sold  by 
avoirdupois  weight,  while  most  photographic  formulas  are 
written  in  apothecaries'  weight.  For  instance,  a  photog- 
rapher buys  negative  cotton  in  ounce  boxes  to  make  col- 
lodion; each  box  contains  437^  grains  (troy),  while  his 
formula  calls  for  480  grains,  an  apothecaries'  ounce.  He 
buys,  however,  16  ounces  or  7,000  grains  in  a  pound,  while 
his  formula  calls  for  but  12  ounces  or  5,760  grains.  Another 
fact  which  the  processworker  is  liable  to  forget  is  that,  in 
fluid  measure,  the  U.  S.  pint  contains  16  ounces  while  the 
British  pint  calls  for  20  ounces. 

DRAGON'S-BLOOD. 
This  resin,  used  so  extensively  in  metal  etching  as  an 
acid  resist,  is  an  exudation  from  trees  of  the  genus  Draccena 
and  others.    It  is  from  the  rattan  palm  (Calamus  draco) 
of  the  East  Indies  that  most  of  the  crimson-red  resin,  used 

171 


172 


horgan's  half-tone 


by  etchers,  comes.  When  in  sticks  it  is  called  reed  dragon's- 
blood,  though  it  is  most  frequently  imported  in  dark  red 
chunks  known  as  lump  dragon's-blood.  It  melts  at  2480  F. 
Its  specific  gravity  is  1.196.  It  is  soluble  in  alcohol,  ben- 
zin,  chloroform,  carbon  bisulphid,  glacial  acetic  acid  and 
caustic  soda  or  potash.  Insoluble  in  kerosene,  petroleum, 
ether,  and  only  sparingly  soluble  in  turpentine  or  ether. 
The  pure  resin  may  be  obtained  by  dissolving  the  powdered 
article  in  alcohol,  filtering  out  the  residue  and  evaporating 
the  alcohol.  For  the  purpose  of  powdering  and  brushing 
against  the  sides  of  etched  lines,  dragon's-blood  is  more  sat- 
isfactory if  not  entirely  pure. 


FISH  GLUE. 

Fish  glue  is  a  common  kind  of  isinglass  and  is  made,  as 
its  name  indicates,  by  boiling  the  heads,  tails  and  skins  of 
fish.  A  preservative  is  used  in  it  to  keep  it  from  putrefac- 
tion. It  is  the  basis  of  the  acid  resist  used  in  copper  etching 
and  called  enamel.   

TO  MAKE  PERCHLORID  OF  IRON  SOLUTION. 
In  case  one  is  out  of  perchlorid  of  iron  for  etching  cop- 
per it  is  well  to  know  that  one  can  prepare  it  by  dissolving 
wire  nails  or  piano  wire  in  four  parts  of  muriatic  acid  to 
one  part  of  nitric  acid.  This  should  be  done  in  a  stone- 
ware vessel,  out  of  doors,  as  the  fumes  are  horribly  dan- 
gerous. The  mass  is  stirred  from  time  to  time  with  a  glass 
rod.  When  the  acids  have  taken  up  all  the  iron  they  will, 
a  solution  is  obtained,  largely  perchlorid  of  iron  with  some 
nitrate  of  iron  and  free  acid,  but  it  will  etch  copper  all  right. 


RETOUCHING  VARNISH. 

When  an  image  is  developed  on  zinc  or  copper,  either  by 
the  albumen  or  enamel  methods,  it  is  necessary  to  examine 
it  carefully,  with  a  magnifying  glass  if  necessary,  to  see 
that  there  are  no  breaks  or  defects  in  the  ink  or  enamel 
images.  If  so,  these  holes  or  defects  must  be  stopped  out 
with  red  sable  brushes  and  a  slow-drying  varnish  that  will 


FACTS  FOR  FOREMEN  AND  FINISHERS 


173 


absorb  etching-powder.  An  etcher  should  have  a  set  of  at 
least  three  red  sable  brushes  ranging  from  the  finest  to,  say, 
a  No.  3. 

The  retouching  varnish  can  be  made  by  softening  a  little 
of  the  etching-ink  with  either  turpentine  and  oil  of  lavender, 
or  both  by  preference.  This  can  be  mixed  to  any  consist- 
ency in  a  small  saucer,  which  is  inverted  when  not  in  use 
so  as  to  escape  dust.  An  etcher  generally  treasures  the  fine- 
pointed  sable  brushes  that  he  has  "  broken  in  "  and  will 
clean  them  out  with  turpentine  at  night  when  he  is  through 
with  them.  There  is  a  retouching  crayon  made  by  Korn 
that  all  etchers  should  have  at  hand. 


VARNISH  FOR  PLATE  BACKING. 
There  is  no  better  varnish  for  protecting  the  back  of 
metal  plates  from  the  action  of  acids  than  asphaltum.  It 
is  easily  prepared  by  dissolving  the  lump  asphalt  in  benzin. 
It  is  well  to  add  a  little  oil  of  lavender  to  prevent  it  drying 
too  brittle.  This  varnish  is  applied  to  the  back  of  metal 
plates,  while  they  are  warm,  with  a  broad  bristle  brush.  It 
is  removed  by  heating  the  plate  and  using  either  strong 
potash  or  benzin.   

REMOVING  MAGNESIA  FROM  FINISHED  HALF-TONES. 

When  an  enameled  copper  plate  is  etched  it  is  customary 
to  fill  in  the  etched  parts  with  magnesia  to  learn  the  state 
of  the  plate.  This  dispenses  with  proof-pulling.  When 
reetching  is  done,  the  magnesia,  though  not  interfering  with 
the  mordant,  combines  with  the  chlorid  of  iron  to  make  a 
solid  substance  which  is  difficult  to  remove  even  with  a  stiff 
brush.  It  can  be  removed  by  laying  the  half-tone  plate  in 
a  weak  nitric  acid  bath  and  then  brushing  the  plate  under 
the  tap.  An  ounce  of  hydrochloric  acid  and  an  ounce  of 
salt  in  ten  ounces  of  water  will  remove  it.  So  also  will  a 
dram  each  of  chromic  and  sulphuric  acids  in  twenty  ounces 
of  water.  In  fact  any  solution  used  for  removing  scum 
from  the  copper  plate  before  etching  will  with  the  aid  of  a 
brush  dislodge  the  magnesia  from  a  finished  copper  plate. 


174 


HORGAN  S  HALF-TONE 


OILS  USED  IN  TRANSFER  INK. 

The  oils  useful  in  transfer  and  etching  inks  may  be 
classified  into  vegetable  and  animal  oils,  drying  and  non- 
drying  oils,  and  solid  oils. 

The  most  useful  oil  is  made  from  linseed,  or  flaxseed. 
Expressed  from  the  flaxseed  cold,  it  is  a  light  yellow  in 
color.  Drawn  from  the  seed  with  heat,  it  is  a  dark  brown 
and  not  so  valuable  as  the  cold-pressed.  It  is  liable  to  be 
adulterated  with  cottonseed  oil,  which  is  not  a  true  drying 
oil  like  linseed.  Boiled  linseed  oil  has  been  heated  to  about 
3000  F.   It  dries  quicker  than  the  raw  oil. 

The  other  drying  oils  are  Scotch  fir-seed  oil,  poppy-seed 
oil,  walnut  oil,  hempseed  oil,  hazel-nut  oil  and  the  oil  from 
tobacco. 

Among  the  non-drying  oils  are  castor  oil,  olive  oil,  mus- 
tard oil  and  rapeseed  oil.  None  of  these  should  be  used 
in  ink. 

The  solid  vegetable  oils  valuable  in  transfer  and  etching 
inks  are :  Bay  wax,  palm  oil,  cocoanut  oil,  Japan  wax,  and 
cocoanut  oil  and  butter. 

The  animal  oils  are  non-drying  oils  and  consequently 
not  so  useful.  Mutton  tallow  is  used  in  transfer  ink,  while 
lard,  neat's-foot  oil,  stearin  (which  is  insoluble  in  cold  alco- 
hol), and  olein,  the  liquid  portion  of  fixed  oils  and  fats  are 
not  recommended  for  transfer  or  etching  inks. 


ACID-PROOF  DUSTING  POWDERS. 

The  etcher  has  a  great  number  of  substances  that  can 
be  finely  powdered  and  used  to  dust  up  the  ink  image  on 
metal  or  be  used  to  brush  against  the  sides  of  the  etched 
line.  Dragon's-blood  leads  in  efficiency.  Then  there  is  the 
old  reliable  asphalt,  which  has  a  tendency  to  cling  together 
and  not  stay  powdered.  Ordinary  resin  or  colophony  makes 
an  excellent  white  powder.    Then  there  is  lac,  or  shellac, 


FACTS  FOR  FOREMEN  AND  FINISHERS  175 

mastic,  sandarac,  dammar  and  copal,  all  with  different  melt- 
ing points,  so  that  combinations  of  these  different  resins 
are  sold  under  various  proprietary  names.  It  is  not  gen- 
erally known  that  after  charging  the  inked  print  on  metal 
with  one  powder,  say  resin,  it  will  take  more  powder  if 
another  powder  is  used  immediately,  say  dragon's-blood. 
And  also  that  graphite  can  be  used  to  advantage  on  top  of  a 
powder  and  before  melting.  That  is  when  "  topping." 


WAXES  AND  RESINS  IN  ETCHING-INK. 

The  waxes  used  in  etching-ink  are:  Beeswax,  which 
should  be  from  the  honeycomb  (usually  adulterated  with 
paraffin  and  other  things)  ;  palm-tree  wax,  carnauba  wax, 
Chinese  and  Japanese  wax. 

The  most  valuable  resins  in  etching-ink  are  asphaltum, 
Canada  balsam,  Burgundy  pitch,  lac,  frankincense,  copaiba 
balsam,  and  colophony  or  resin. 


STOPPING-OUT  VARNISH. 

The  varnish  used  by  finishers,  or  reetchers,  for  stopping 
out  portions  of  the  plate  before  reetching,  is  usually  made 
of  shellac.  A  saturated  solution  of  ordinary  unbleached 
shellac  should  be  kept  in  one  bottle  and  some  of  this  diluted 
with  alcohol  for  use.  It  can  be  dyed  a  strong  blue  so  as  to 
show  strongly  on  copper,  or  dyed  red  if  used  on  zinc. 

Chinese  or  Japanese  brushes  in  bamboo  handles  are 
admirable  for  use  in  stopping  out.  When  not  in  use  the  tips 
can  be  left  in  alcohol. 

To  remove  stopping-out  varnish,  alcohol  had  better  be 
used. 


AQUATINT  GRAIN. 

There  are  many  times,  outside  of  tint-blocks,  in  which 
the  processworker  would  like  to  secure  a  grain  on  a  plate 
when  a  grain  box  is  not  at  hand.  It  can  be  done  by  flowing 
on  the  plate  a  mixture  of  resin  and  alcohol.   As  the  alcohol 


176 


horgan's  half-tone 


evaporates,  the  resin  forms  in  fine  grains  all  over  the  plate. 
These  grains  can  be  secured  firmly  to  the  plate  by  heat. 

Another  method  is  to  lay  a  wax  ground  on  the  plate, 
and  while  the  ground  is  soft  dust  over  it  fine  table  salt, 
which  sinks  into  the  wax.  When  the  plate  is  placed  in  the 
acid  the  salt  dissolves  away,  leaving  "  punctures  "  in  the 
wax  resist. 

Still  a  more  delicate  way  is  to  oil  the  plate  and  sift  pow- 
dered sulphur  over  it.  The  grains  of  sulphur  etch  the  cop- 
per enough  to  show  a  grain  in  printing. 


TO  COPPER-PLATE  ZINC. 

When  the  writer  began  to  introduce  zinc  etchings  in 
New  York  in  1881  the  printers  would  not  receive  them 
because  they  claimed  they  would  not  take  ink,  so  the  zinc 
was  copper-faced  in  the  following  manner: 

Make  two  solutions,  one  a  saturated  solution  of  copper 
sulphate  and  the  other  a  saturated  solution  of  cyanid  of 
potassium.  Pour  the  cyanid  solution  into  the  copper  solu- 
tion, being  careful  when  doing  so  to  do  it  out  of  doors  and 
to  windward  of  the  mixture,  as  the  fumes  that  result  are 
fatal  if  taken  into  the  lungs. 

Scrub  the  surface  of  the  zinc  plate  thoroughly  with 
potash,  and  place  this  in  the  cyanid  of  copper  solution,  when 
it  will  almost  immediately  take  on  a  perfect  coating  of  pure 
copper.  Remove  and  wash  well  under  the  tap  and  dry  with 
a  clean  cloth. 


TO  PREVENT  OXIDATION  OF  ZINC  ETCHINGS. 
Many  printers  complain  that  zinc  engravings  oxidize. 
This  is  caused  by  the  lye  used  to  clean  the  etchings  after 
printing.  Lye  corrodes  zinc  when  it  does  not  injure  type 
metal.  Zinc  etchings  should  be  cleaned  with  benzin  after 
printing  from  them.  If  they  are  to  be  put  away  for  use 
a  long  time  later  they  should  be  heated  and  rubbed  over 
with  wax.  When  the  etchings  are  to  be  used  the  wax  can  be 
removed  by  again  heating  and  cleaning  with  turpentine. 


POINTERS  FOR  THE  PHOTOGRAPHER, 

INCLUDING 


SOME  STANDARD  FORMULAS  AND  METHODS  HE 
SHOULD  KNOW. 


PHOTOGRAPHING  ON  WOOD. 

The  sides  of  the  block  are  rubbed  with  heated  wax  or 
paraffin.  This  is  to  keep  moisture  from  injuring  the  wood. 
Three  solutions  are  kept  in  stock  ready  for  use : 

1.  Gelatin  16  grains  to  the  ounce  of  water 

2.  Nitrate  of  silver  80  grains  to  the  ounce  of  water 

3.  Citric  acid   40  grains  to  the  ounce  of  water 

The  white  of  an  egg  is  beaten  to  a  froth  and  left  stand- 
ing over  night.    Now,  to  sensitize  the  wood  block,  take  — 

White  of  egg   1  dram 

Gelatin  solution   yi  dram 

Best  zinc  white  %  ounce 

Ammonium  chlorid   5  grains 

Rub  these  into  a  paste  in  a  glass  mortar,  and  while  rub- 
bing drop  slowly  into  the  paste  thirty  minims  of  the  citric 
acid  solution  and  thirty  minims  of  the  nitrate  of  silver  solu- 
tion. Paint  this  on  the  block,  dry  in  the  dark  and  print  as 
usual.  Tone  and  fix  if  you  wish,  though  many  simply  fix 
and  wash  off  with  hypo.  Dry  the  moisture  from  the  block 
with  soft  chamois.  This  gives  a  brilliant  print,  prevents 
the  wood  from  injury  by  chemicals  and  leaves  scarcely  any 
film  to  interfere  with  the  graver;  all  of  which  are  appre- 
ciated by  the  careful  wood  engraver. 


BLEACHING  SILVER  PRINTS  WITH  CUTTING  SOLUTION. 

It  is  not  generally  known  that  the  regular  "  cutting " 
solution,  a  mixture  of  iodin,  iodid  of  potassium  and  cyanid 
of  potassium,  makes  a  good  bleaching  solution  for  photo- 
graphic prints  that  have  been  drawn  with  waterproof  ink. 
Farmer's  solution  will  also  bleach  them. 


12 


177 


178 


horgan's  half-tone 


PLAIN  PHOTOGRAPHIC  PAPER  — TO  MAKE  AND  USE. 

An  artist  can  prepare  his  own  salted  photographic  paper 
and  it  will  keep  forever  if  he  uses  this  simple  formula : 


Take  a  smooth,  good  quality  pure  linen  paper,  if  it  is  to 
be  used  for  pen-and-ink  drawing,  or  a  rough  paper,  like 
Whatman's  drawing-paper,  if  for  washwork,  and  immerse  it 
in  the  above  solution  while  warm. 

When  the  paper  is  soaked,  with  this  liquid  hang  it  up  to 
dry.  It  will  keep  indefinitely.  To  sensitize  it,  in  a  dark- 
room, swab  over  its  surface,  with  a  wad  of  absorbent  cotton : 

Water    i  ounce 

Nitrate  of  silver  50  grains 

Citric  acid   15  grains 

After  printing  under  a  negative,  fix  in  one  ounce  of 
hyposulphit  of  soda  in  ten  ounces  of  water  and  wash  well. 


BLEACHING  PHOTOGRAPHIC  PRINTS  WHITE. 

demon's  matt-surface  paper  is  sensitized  by  rubbing 
over  it,  with  a  tuft  of  cotton,  a  solution  of  forty  grains  of 
nitrate  of  silver  and  dried.  A  photographic  print  is  made 
upon  it  and  fixed  in  hyposulphit  of  soda.  Washed  and 
dried  it  will  be  found  one  of  the  finest  mediums  for  draw- 
ing upon.  After  the  drawing  is  finished  it  can  be  bleached 
a  permanent  white  by  flowing  over  it  a  solution  of 

Mercury  bichlorid  1  ounce 

Water  5  ounces 

Alcohol   1  ounce 

Hydrochloric  acid  1  dram 

If  the  drawing  is  made  with  a  nonwaterproof  ink,  then 
alcohol  is  substituted  for  the  water  in  the  formula.  When 
the  bleaching  solution  is  poured  off,  the  drawing  is  washed 
under  the  tap  to  remove  the  mercury. 


Water   

Gelatin  

Chlorid  of  ammonium 


12  grains 
8  grains 


1  ounce 


POINTERS  FOR  THE  PHOTOGRAPHER 


179 


BLUE-PRINTS  —  CYANOTYPE. 

The  ferroprussiate  paper  used  by  architects,  commonly 
called  blue-print  paper,  can  be  prepared  of  a  better  quality 
than  any  purchasable  by  using  the  following  formula : 

Water  10  ounces 

Gum  arabic   i  ounce 

Red  prussiate  of  potash   I  ounce  20  grains 

Citrate  of  iron  and  ammonia   1  ounce  20  grains 

This  solution  can  be  applied  to  well-sized  or  highly  cal- 
endered paper  with  a  flat  brush,  but  it  must  be  dried  in  the 
dark. 


TO  BLEACH  BLUE-PRINTS. 

If  waterproof  ink  is  used  to  draw  upon  blue-prints  they 
can  be  bleached  white  by  flowing  with  a  strong  solution 
of  saleratus  or  baking  soda  (carbonate  of  soda).  Of 
course,  cyanid  of  potassium,  dilute  ammonia  and  other  alka- 
lies will  bleach  blue-prints,  but  the  saleratus  is  least  harmful 
to  use.  Potassa  solution,  U.  S.  P.  (potassium  hydroxid), 
may  also  be  used. 


COST  OF  WOOD  ENGRAVING. 

The  writer  was  requested  by  the  Alumni  Association 
of  one  of  the  leading  colleges  in  the  United  States  to  have 
engraved  for  them  in  wood  a  portrait  of  their  retiring  presi- 
dent. A  well-known  portrait  engraver  was  seen  who  meas- 
ured the  photograph  carefully  and  found  it  was  4  by  5^2 
inches,  an  engraving  of  which,  that  size,  he  said  would  cost 
from  $230  to  $240.  An  engraving  of  the  portrait  enlarged 
to  8  by  10  inches  would  cost  $480,  and  larger  sizes  in  pro- 
portion, or  $10  for  each  square  inch.  Proofs  would  cost 
$1  each,  and  the  smaller  engraving,  4  by  5^2  inches,  could 
be  finished  in  about  seven  weeks.  If  these  are  the  prices 
of  wood  engraving  in  competition  with  photoengraving, 
what  would  be  the  charges  for  wood  engraving  if  methods 
of  engraving  through  the  aid  of  photography  had  not  been 
discovered  ?  With  the  Japanese  schoolboy,  "  I  ask  to  know." 


BICHROMATE  POISONING  REMEDIES. 


So  many  processworkers  suffer  from  sores  on  their 
hands  from  bichromate  poisoning  that  the  following  spe- 
cifics should  be  known.   To  allay  irritation  use : 

Alcohol  (pure  grain)   I  ounce 

Glycerin   y2  ounce 

Carbolic  acid  (pure)   I  dram 

Nitrate  of  mercury  ointment  is  used  to  heal  up  the  old 
£ores.  In  the  U.  S.  Pharmacopseia  it  is  "  Unguentum 
Hydrargii  Nitratis,"  and  is  compounded  as  follows : 

Nitrate  of  mercury  160  grains 

Nitric  acid    I  ounce 

Prepared  lard   I  ounce 

Olive  oil   3  ounces 

To  prepare  this  ointment,  dissolve  the  mercury  in  the 
nitric  acid.  By  the  aid  of  gentle  heat,  melt  the  lard  in  the 
olive  oil  in  a  vessel  standing  in  hot  water.  Bring  the  water 
in  the  outer  vessel  to  a  boil,  and  after  heating  the  mercury 
solution  to  the  boiling  point,  pour  the  latter  into  the  oil,  stir- 
ring all  the  while  with  a  glass  rod.  If  the  mixture  does  not 
froth  up  at  once,  increase  the  heat  until  it  does,  and  then 
stir  until  cold. 

Another  preventive  of  bichromate  poisoning  is  to  wash 
the  hands  with  good  castile  soap  after  using  bichromate. 
Dry  the  hands  thoroughly  and  then  rub  into  them  a  few 
drops  of  the  alcohol,  glycerin  and  carbolic  solution  recom- 
mended above. 

VIOLET  RAYS  INJURE  EYESIGHT. 

The  violet  rays  from  the  enclosed  arc  lamp,  not  being 
bright,  are  not  suspected  of  being  injurious  to  eyesight  until 
the  injury  is  done.  Yellow  glasses  such  as  are  used  to  pre- 
vent snow-blindness  will  protect  the  photographer's  eyes 
from  injury.  It  is  the  ultra  violet  rays  in  sunlight  that 
burn  the  skin  of  the  "  summer  girl "  or  the  process  man, 
but  after  continuing  in  sunlight  for  several  days  nature  fur- 
nishes a  coat  of  tan,  which  is,  after  all,  but  a  yellow  filter. 

ISO 


TO  CARE  FOR  A  LITHOGRAPHIC  ROLLER 


PROPERLY 

IS  A  MOST  IMPORTANT  MATTER  IN  SEVERAL  OF  THE 
PHOTOMECHANICAL  PROCESSES. 


LITHOGRAPHIC  ROLLER  PREPARATION. 

A  good  smooth-skin  leather  litho  roller  is  a  treasure, 
not  only  to  the  lithographer  but  to  the  process  engraver, 
for  laying  a  proper  film  of  etching-ink  on  a  zinc  plate  that 
has  an  albumen  print  on  it. 

Litho  hand  rollers  are  made  of  wood  like  the  house- 
wife's rolling  pin,  then  they  are  wrapped  first  with  several 
thicknesses  of  fine  flannel  and  covered  on  the  outside  with 
calfskin.  The  seam  in  the  skin  should  be  scarcely  visible 
when  the  roller  is  new,  and  after  much  use  it  will  disappear 
entirely  if  the  roller  is  properly  taken  care  of. 

To  break  in  a  new  litho  roller  the  leather  must  first  be 
saturated  with  an  oil  and  then  with  litho  varnish.  It  is  an 
operation  that  takes  time.  Castor  oil  is  excellent  to  begin 
the  treatment  with.  On  a  clean  ink  slab  spread  a  little 
castor  oil  and  roll  up  the  roller  in  this  several  times  during 
the  day  and  leave  it  over  night  if  possible.  Next  day  the 
castor  oil  should  be  soaked  into  the  leather.  Wipe  any 
surplus  oil  from  the  roller  and  roll  it  up  in  middle  linseed 
oil  varnish  several  times  during  the  second  day  and  allow 
the  varnish  to  be  absorbed  by  the  roller  over  night.  This 
should  be  repeated  for  several  days  until  the  leather  will 
not  absorb  any  more  varnish. 

When  using  etching-ink  on  the  roller,  warm  the  ink  slab, 
take  but  a  little  etching-ink  on  the  end  of  the  palette-knife 
and  heat  it  before  spreading  it  in  a  broad  line  across  the 
ink  slab.  Roll  this  ink  well  into  the  roller,  turning  the  lat- 
ter occasionally  so  as  to  get  a  perfectly  even  coating  on  the 
slab. 

The  writer  never  used  benzin,  turpentine  or  other  fluid 
than  varnish  on  the  roller  to  clean  it.    He  merely  softened 

181 


182 


HORGAN  S  HALF-TONE 


old  ink  on  the  roller  with  litho  varnish  and  then  with  the 
back  of  a  knife  scraped  the  roller,  with  the  grain  of  the 
skin,  free  of  ink.  Every  Saturday  the  roller  was  rolled  up 
in  litho  varnish  and  left  until  Monday  to  soften.  Then 
it  was  scraped  and  rolled  up,  with  either  etching-ink  or 
lithographic  ink,  depending  on  whether  he  was  going  to 
use  it  for  photolithographic  work  or  for  etching-ink  on 
zinc,  and  the  roller  was  always  in  excellent  condition.  When 
not  in  use  it  must  be  kept  in  a  box,  resting  on  its  handles, 
and  free  from  dust. 


PRINTING  ON  STONE  WITHOUT  A  FRAME. 

As  the  use  of  a  printing-frame  for  getting  a  photo-print 
on  stone,  from  a  negative  on  glass,  is  not  feasible,  it  is  cus- 
tomary to  strip  the  negative  film  from  its  glass  support  and 
bring  it  into  contact  with  the  sensitive  coating  on  stone  by 
the  use  of  vaseline  or  some  transparent  non-drying  oil  that 
has  no  effect  on  the  sensitive  gelatin  or  albumen  coating  on 
the  stone.  The  negative  is  stripped  from  the  glass  by  the 
method  described  elsewhere,  and  the  side  that  is  to  come 
into  contact  with  the  stone  is  smeared  over  with  vaseline, 
glycerin,  castor  oil  or  olive  oil,  taking  care  not  to  form 
small  bubbles.  The  film  is  then  turned  over  on  the  sensi- 
tized and  slightly  warmed  stone  and  slid  into  its  proper 
place,  after  which  a  thin  sheet  of  paper  is  laid  over  it  and 
the  surplus  oil  squeegeed  out  from  between  the  film  and 
stone,  with  a  roller  squeegee  by  preference.  The  oil  is  then 
cleaned  from  the  surface  of  the  negative  film  with  a  soft 
rag  and  benzin.  After  printing  in  sunlight,  electric  light 
(or,  if  a  cloudy  day,  see  that  the  light  reaches  the  film  at 
as  near  right  angles  as  possible),  peel  the  negative  carefully 
from  the  stone,  in  the  darkroom,  wipe  off  the  oil  with  a 
soft  rag  and  benzin  and  then  develop  with  water.  This 
method  can,  of  course,  be  applied  to  metal  plates  too  large 
for  the  printing-frames  at  hand. 


FROM  A  NEGATIVE  ETCHED  WITH  NEEDLE  POINTS. 
New  York  Daily  Graphic,  June  26,  1873. 


NEGATIVES  ETCHED  BY  HAND. 


ALSO 

THE  VARNISH  FOR  SCREEN  RULING  HERE  USED  IS  A 
*     MOST  VALUABLE  FORMULA. 


There  is  a  little-known  method  of  producing  negatives 
mechanically  that  was  practiced  on  the  New  York  Daily 
Graphic  from  1873  to  1876.  It  has  some  advantages  for 
exceedingly  fine  engraving  and  for  scientifically  accurate 
work.    It  is  here  published  for  the  first  time. 

Instead  of  drawing  in  waterproof  ink  over  a  photograph 
on  plain  paper,  as  described  elsewhere,  a  photographic  posi- 
tive is  made  from  the  copy  on  glass,  similar  to  a  magic- 
lantern  transparency.  This  positive  must  be  the  exact  size 
of  the  intended  reproduction  of  the  photograph,  engraving 
or  lithograph.  It  is  better  to  make  this  positive  by  the 
collodion  process,  either  wet  or  dry,  though  a  gelatin  dry 
plate  can  be  used. 

A  MOST  VALUABLE  VARNISH  FORMULA. 

When  the  positive  is  dry  it  is  slightly  warmed  and  flowed, 
on  the  film  side,  with  the  following  artists'  etching  varnish : 


A.  Powdered  Egyptian  asphalt   4  ounces 

Turpentine,  U.  S.  P   20  ounces 

B.  Burgundy  pitch  (from  Norway  spruce)   1  ounce 

Turpentine,  U.  S.  P   12  ounces 

Beeswax,  pure  il/2  ounces 


It  is  necessary  that  all  the  ingredients  of  this  varnish  be 
pure  and  no  "  substitutes "  used  instead  of  them.  The 
method  of  preparation  is  this:  The  four  ounces  of  pow- 
dered asphalt  is  dissolved  in  twenty  ounces  of  spirits  of 
turpentine.  The  one  ounce  of  Burgundy  pitch  is  dissolved 
in  the  twelve  ounces  of  turpentine  with  the  aid  of  slight 
heat,  and  then  the  one  and  one-half  ounces  of  pure  beeswax 
is  added.    The  solutions  A  and  B  are  mixed,  and  then  fil- 

183 


184 


horgan's  half-tone 


tered  several  times  before  using.  Porcelain-lined  pots  are 
recommended  for  the  mixing  vessels  and  glass  rods  for 
stirring  purposes. 

ETCHING  THE  NEGATIVE. 

In  a  warm  place,  free  from  dust,  the  positive  is  flowed 
with  this  varnish  just  as  if  it  were  collodion.  It  is  allowed 
to  dry,  by  the  evaporation  of  the  turpentine,  in  an  oven  or 
warm  place,  after  which  it  is  allowed  to  cool,  when  the  artist 
will  find  it  to  be  hard  and  a  delightful  medium  to  etch  in 
with  a  needle  point. 

The  artist  is  provided  with  a  set  of  etchers'  steel  points. 
He  places  the  positive  in  a  photographers'  retouching  stand, 
large  enough  for  him  to  turn  the  positive  around  in  so  as 
to  use  his  needles  in  any  direction.  All  the  light  comes 
through  the  positive,  which  he  can  see  beautifully  clear 
through  the  golden-hued  transparent  varnish  which  covers 
it.  Should  the  subject  be  a  portrait,  he  traces  through  the 
ground  just  as  an  artist  etcher  does  through  the  etching 
ground  on  the  copper  plate,  with  the  advantage  that  he  has 
the  portrait  to  guide  him  and  there  is  no  trouble  in  getting 
correct  drawing.  The  points  slide  so  easily  over  the  smooth 
glass  that  the  lines  possess  a  grace  and  freedom  of  execu- 
tion that  is  not  possible  by  any  other  method. 

ADMIRABLE  FOR  SCIENTIFIC  WORK. 

The  line  engraved  in  this  manner  possesses  a  sharpness, 
crispness  and  smoothness  of  edge  admirably  adapted  for 
scientific  work.  Most  accurate  work  can  be  done  with  these 
mechanically  engraved  negatives,  for  at  no  stage  in  the 
process  is  there  any  danger  of  distortion.  The  artist  traces 
the  positive  exactly,  and  from  this  hand-made  negative  the 
print  is  made  upon  the  metal  direct.  Furthermore,  lines  can 
be  engraved  of  most  extreme  fineness,  and  in  number  to 
the  inch  so  great  as  not  to  be  counted  without  a  magnifier. 

VARNISH  FOR  SCREEN  MAKING. 

The  formula  for  varnish  used  in  this  process  is  the  one 
used  in  screenmaking  for  coating  the  glass  before  ruling 


NEGATIVES  ETCHED  BY  HAND 


185 


them  with  a  diamond  point.  It  will  be  found  that  this  var- 
nish permits  cross-ruling  without  chipping,  so  that  screens 
for  the  rotary  photogravure  process  can  be  made  through 
its  use.  Glass  so  ruled  may  be  used  either  at  once  for  a 
screen  or  the  glass  can  be  etched  with  hydrofluoric  acid, 
the  varnish  removed,  and  the  etched  lines  on  the  glass  filled 
in  with  the  finest  possible  vine-carbon  printing-ink.  In 
making  the  ordinary  cross-line  screen  it  is  better  to  rule  two 
single-line  screens  and  cement  them  to  each  other  at  right 
angles  with  Canada  balsam,  for  the  reason  that  in  attempt- 
ing to  etch  crossed  lines  in  glass  with  hydrofluoric  acid  the 
sharp  corners  of  the  squares  are  rounded  by  the  acid. 

FACTS  CONCERNING  SCREENS. 

CLEANING  HALF-TONE  SCREENS. 

Japanese  or  Chinese  silk,  from  which  all  the  size  has  been 
removed  by  washing  in  hot  water,  is  the  best  material  to 
clean  half-tone  screens  with.  If  there  should  be  some  dirt 
on  the  screen,  which  moistening  with  the  breath  and  rubbing 
with  the  silk  will  not  remove,  it  can  be  softened  with  a  few 
drops  of  alcohol  and  rubbed  with  soft  silver  tissue-paper, 
followed  with  the  silk.  The  cleaning  should  be  done  while 
the  screen  lies  flat  on  a  soft  support.  No  rouge,  rotten- 
stone,  whiting  or  other  polishing  powder  should  be  used 
on  a  screen.  The  silk  used  to  clean  with  should  be  kept  in 
a  tight  covered  box  when  not  in  use. 


TO  PREVENT  SCREEN  SWEATING. 

This  is  one  of  the  "  bugaboos  "  of  the  half-tone  negative- 
maker  in  winter  if  the  lightroom  is  not  of  the  same  tempera- 
ture as  the  darkroom.  The  wet  collodion  plate  is  sensitized 
in  a  warm  silver  bath  and  then  placed  with  a  cold  screen 
in  a  camera  in  a  cold  lightroom  for  a  long  exposure,  with 
the  result  that  sweat  forms  on  the  side  of  the  screen  nearest 
the  wet  plate  and  the  result  is  a  fuzzy  negative.   The  reme- 


186 


horgan's  half-tone 


dies  are  many.  One  is  to  polish  the  screen  with  "  La 
Crystaline,"  a  medium  used  in  cold  countries  to  prevent 
sweat  forming  on  spectacle  lenses  when  going  from  out 
of  doors  to  a  warm  interior.  Polishing  with  wax  and  gly- 
cerin are  also  recommended.  Keeping  a  hot  water  bottle 
in  the  camera  box  is  another  remedy,  while  the  best  plan 
of  all  is  to  keep  darkroom,  lightroom,  silver  bath  and  screen 
all  at  as  nearly  the  same  temperature  as  possible. 


MEZZOGRAPH  SCREEN. 

Some  of  the  points  to  be  observed  when  using  a  mezzo- 
graph  screen  are  the  following:  The  screen  distance  is  of 
the  most  importance  and  can  be  determined  only  by  observ- 
ing the  mezzograph  image  formation  on  the  ground  glass 
with  a  powerful  magnifier.  A  diaphragm  of  f/32  should 
be  used,  after  the  copy  is  focused  with  an  open  lens.  With 
the  small  stop  start  with  the  screen  as  close  to  the  ground 
glass  as  possible,  and  when  the  curious  pattern  of  the 
screen  appears  sharpest,  that  is  the  proper  distance.  The 
exposure  is  surprisingly  short.  Do  not  overdevelop,  and 
clear  the  negative  of  any  veil  or  fog  with  the  cutting  solu- 
tion before  intensification  with  copper  and  silver.  The 
screen  distance  need  hardly  be  changed  with  the  camera 
extension  nor  with  change  of  stops.  It  is  better  when  print- 
ing on  copper  to  use  a  very  thin  enamel. 


WHERE  THE  MEZZOGRAPH  SCREEN  IS  MOST  USEFUL. 

The  mezzograph  screen  is  far  superior  to  the  ordinary 
half-tone  screen  when  reproducing  copy  which  is  either  a 
half-tone  print,  a  wood  engraving,  or  a  steel  engraving. 
Where  the  cross-line  screen  would  give  a  pattern  the  mezzo- 
graph  screen  reproduces  without  pattern.  For  the  tint 
plate  in  duotypes  it  is  most  useful,  and  in  four-color  work 
many  firms  use  it  for  the  yellow  plate.  In  the  reproduction 
of  grained  leather,  or  stone  and  landscapes,  the  mezzograph 
screen  is  of  more  service  than  the  cross-line  one. 


PROGESSWORKERS  MAY  BE  JAILED  OR 
FINED  FOR  THESE  REASONS. 


WHEN  IS  A  PICTURE  UNFIT  FOR  PUBLICATION? 

"  This  question  was  lately  brought  to  a  practical  issue 
in  New  York,  and  squarely  met  by  Stephen  H.  Horgan,  art 
editor  of  the  New  York  Tribune/'  —  W.  I.  Scanlan,  Pen- 
rose's Pictorial  Annual,  1904-05,  page  71. 

"  The  increasing  use  of  semidraped  and  nude  figures  in 
the  illustration  of  advertisements,  booklets,  and  other  pub- 
licity matter  brings  up  a  point  which  is  of  practical  interest 
to  photographers  everywhere.  The  question,  What  makes 
a  photograph  unfit  for  publication?  is  not  always  easily 
decided;  but  upon  its  decision  often  a  fine  of  $5,000  may 
depend.  In  The  Inland  Printer  for  June  (1904)  Mr.  Ste- 
phen H.  Horgan,  the  art  editor  of  the  New  York  Tribune, 
answers  this  question  so  tersely  and  so  much  to  the  point, 
that  its  publication  may  serve  to  keep  some  photographer 
out  of  trouble."  —  John  A.  Tennant,  editor,  Photo-Minia- 
ture. 

"  This  question  has  long  demanded  an  answer,  and  one 
which,  with  the  increasing  use  of  photography  in  all  sorts 
and  kinds  of  advertising  matter,  is  becoming  more  important 
every  day.  We  gladly  give  space  in  this  journal  to  Mr. 
Horgan's  rule  governing  the  subject,  believing  it  to  be  in 
the  best  interest  of  all  that  is  best  in  photography."  —  Wil- 
son's Photographic  Magazine. 

The  rule,  printed  first  in  The  Inland  Printer,  was  as 
follows : 

"  Photographs  of  human  beings  in  costumes  or  poses  in 
which  they  would  not  appear  in  public  are  liable  to  be  unfit 
for  publication  in  an  ordinary  newspaper." 

"  This  seems  about  as  reasonable  a  definition  of  what 
makes  a  picture  unfit  for  publication  as  we  are  likely  to  get." 
—  British  Journal  of  Photography. 

Section  3893  of  the  Revised  Statutes  of  the  United 

187 


188 


horgan's  half-tone 


States  forbids  the  mailing  of  a  publication  containing  an 
indecent  picture  and  fixes  the  penalty,  upon  conviction,  of 
$5,000  fine,  or  five  years  at  hard  labor,  or  both. 


GOVERNMENT  MONEY  OR  STAMPS  MUST  NOT  BE 
PHOTOGRAPHED. 

All  processworkers  should  know  that  the  present  law 
makes  it  a  crime  to  photograph  even  a  portion  of  any  stamp, 
bill  or  certificate  of  the  United  States  or  any  other  country. 
The  crime  is  punishable  with  heavy  fines  and  punishment 
for  a  long  term  of  years.  By  an  addition  to  the  law, 
approved  February  10,  1901,  "  Every  person  who  has  in 
possession  any  business  card,  notice,  device,  print  or  impres- 
sion, or  any  other  thing  whatsoever,  whether  of  metal  or 
any  other  thing  whatsoever,  in  likeness  or  similitude,  as  to 
design,  color,  or  the  description  thereon,  of  any  of  the  coins 
of  the  United  States,  or  any  foreign  government,  shall,  upon 
conviction  thereof,  be  punished  by  a  fine  not  to  exceed  $100." 
It  will  be  seen  by  this  that  the  reproduction  of  new  postage 
stamps  is  forbidden  and  also  the  drawing  of  bills  or  coins  in 
a  cartoon.   

COPYRIGHT  LAW  PENALTIES. 

Every  processworker  should  know  that  Section  25  of 
the  copyright  law  thus  specifies  the  fines  which  may  be 
imposed  for  the  reproduction  of  a  copyrighted  object  with- 
out permission : 

"  In  the  case  of  a  painting,  statue,  or  sculpture,  $10  for 
every  infringing  copy  found  in  the  possession  of  the 
infringer  or  his  agents  or  employees.  In  the  case  of  any 
other  object  reproduced  the  penalty  is  $1  for  every  infring- 
ing copy  made  or  sold  by  or  found  in  the  possession  of  the 
infringer  or  his  agents  or  employees.  In  the  case  of  a  news- 
paper reproduction  of  a  copyrighted  photograph  the  dam- 
ages shall  not  exceed  the  sum  of  $200  or  be  less  than  $50, 
and  in  no  other  case  exceed  the  sum  of  $5,000  nor  be  less 
than  the  sum  of  $250." 

Full  costs  are  added  in  every  case  to  damages. 


DIRECT  PROCESS  WITH  NORWICH  FILM. 
Ozias  Dodge,  Norwich,  Conn. 


THE  "DIRECT  PROCESS"  WITH  NORWICH 

FILM. 

This  process  was  the  outcome  of  experiments  carried 
on  by  Ozias  Dodge,  the  painter-etcher,  of  Norwich,  Con- 
necticut. As  at  first  practiced  it  consisted  of  a  grained 
transparent  sheet  on  which  an  original  drawing  was  exe- 
cuted with  an  ordinary  pencil.  This  sheet  was  subsequently 
flowed  with  collodion  to  protect  the  drawing.  From  this 
positive  drawing  on  its  transparent  support  a  negative  print 
was  obtained  on  a  sensitized  copper  plate  which  was  etched 
intaglio.  The  impression  from  this  intaglio  plate  was  an 
exact  reproduction  of  the  pencil  drawing. 

Later  Mr.  Dodge  devised  a  method  of  making  relief 
plates  from  the  drawing  on  the  transparent  sheet,  all  of 
his  processes  being  covered  by  patents  in  this  and  other 
countries.  In  his  relief-plate  method  the  picture  is  drawn 
with  a  pencil  or  ink  that  is  soluble  in  gasoline  or  similar 
solvent.  Or,  the  picture  may  be  printed  in  a  lithographic 
ink  on  his  transparent  sheet  known  as  the  "  Norwich 
Film."  The  "  Norwich  Film "  containing  the  picture  is 
next  covered  with  a  red  and  yellow  varnish.  This  varnish  is 
so  arranged  hygroscopically  that  it  will  penetrate  the  sheet 
to  a  certain  depth  in  proportion  to  the  density  of  the  image. 
The  next  step  is  to  develop  a  negative  image  in  the  red  and 
yellow  varnish.  This  is  done  with  gasoline,  which  removes 
every  particle  of  the  original  drawing  or  impression,  leav- 
ing the  varnish  transparent  only  where  the  image  was,  and 
thus  produces  a  perfect  negative  of  the  original  drawing  or 
impression.  This  negative  can  be  used  for  any  purpose  in 
processwork. 

The  process  is  especially  useful  in  making  up  tint-blocks 
from  a  key-plate.  The  material  being  highly  transparent, 
it  is  easy  to  obtain  register  when  making  color  plates. 
Further,  the  transparent  material  is  so  thin  that  negatives 
made  on  it  can  be  printed  from  either  side,  which  supplies 
the  reversed  negative  required  for  the  offset  press. 

189 


190  horgan's  half-tone 

TO  PHOTOGRAPH  KEY-PLATES  ON  ZINC. 

There  are  two  ways  of  photographing  a  drawing  on 
plain  zinc  so  as  to  leave  only  a  stain  on  the  metal,  that  tints 
in  ink  can  be  laid  for  color  plates,  or  an  artist  can  stipple 
the  tints  on  the  metal. 

One  method  shows  the  image  in  bright  polished  zinc  on 
a  gray  ground  and  the  other  gives  a  black  image  with  a 
gray  ground.    The  first  one  is  more  frequently  used. 

In  both  cases  an  inked  albumen  print  is  made  on  the 
zinc  as  described  in  "  Line  Etching."  In  the  first  method 
the  inked  albumen  print  is  made  on  a  polished  sheet  of  zinc, 
dusted  with  resin  and  heated  slightly ;  then  it  is  put  into 
a  graining  bath  and  given  a  beautiful  gray  matt  surface 
everywhere  but  where  the  ink  image  is.  When  the  gray 
background  is  right,  wash  the  plate  under  the  tap,  dry  and 
clean  off  the  inked  image  with  potash,  when  the  print  on 
zinc  will  be  seen  dark  polished  zinc  on  a  gray  ground. 

With  the  other  method  the  zinc  is  cleaned  thoroughly 
and  brushed  over  with  chlorid  of  antimony  —  butter  of 
antimony  it  is  commonly  called.  This  turns  the  zinc  a 
beautiful  blue-black.  The  zinc  is  then  washed  and  dried 
and  an  inked  albumen  print  made  upon  it.  This  is  resined 
and  heated,  as  before,  after  which  it  is  rocked  in  the  grain- 
ing bath.  This  bath  clears  away  the  black  stain  from  the 
zinc,  leaving  a  gray  in  its  place,  and  when  the  inked  image 
is  cleared  off  with  potash  it  will  be  seen  black  against  a 
gray  ground.   

WEIGHTS  OF  SHEET  METALS  PER  SQUARE  FOOT. 
The  approximate  weight  of  the  sheet  metals  used  in 
engraving  are  as  follows,  the  gauge  being  Stubbs' :  14-gauge 
zinc  weighs  45  ounces  per  square  foot ;  15-gauge,  43  ounces, 
and  16-gauge,  39  ounces. 

Copper,  14-gauge,  weighs  64  ounces  a  square  foot ; 

15-  gauge  weighs  56  ounces,  and  16-gauge,  48  ounces. 
Brass,   12-gauge,  weighs  66  ounces  a  square  foot; 

14-gauge  weighs  60  ounces;   15-gauge  weighs  53  ounces; 

16-  gauge,  45  ounces,  and  17-gauge,  40  ounces. 


UNITED  STATES  WEIGHTS  AND  MEASURES. 


APOTHECARIES'  WEIGHT. 
Usually  adopted  in  formulas. 

20  grains  =  I  scruple  =  20  grains 
3  scruples  =  1  dram  =  60  grains 
8  drams    =  1  ounce   —    480  grains 

12  ounces   =  1  pound  =  5,760  grains 

FLUID  MEASURE. 

60  minims  ==  1  fluid  dram 

8  drams  =  1  fluid  ounce 
16  ounces  =  1  pint 

8  pints     =  1  gallon 

APOTHECARIES'  WEIGHT. 

Pound.     Ounces.    Drams.     Scruples.      Grains.  Grams. 

1     =     12     =     96     =     288     =     5,760  =  373-24 

1     =      8     =      24     =       480  =  31.10 

1     ==       3     ~        60  =  3.89 

1     —        20  =  1.30 

1  =  .06 
The  pound,  ounce  and  grain  are  the  same  as  in  troy  weight. 

AVOIRDUPOIS  WEIGHT. 
By  which  all  chemicals  are  usually  sold. 
27M  grains  =  1  dram  =     27M  grains 
16     drams  =  1  ounce  =    437^  grains 
16     ounces  =  1  pound  =7,000  grains 

AVOIRDUPOIS  WEIGHT. 

Pound.    Ounces.      Drams.    Grains  (Troy).  Grams. 

1     =     16     =     256     =     7,000        =  453-6o 

1     =      16     =       437.5      =  28.35 

1     =        27.34     =  177 

UNITED  STATES  FLUID  MEASURE. 

Gal.  Pts.     Ozs.       Drams.       Mins.         Cub.  In.  Grains.  Cub.  C.  M. 

1  =  8  ==  128  =  1,024  =  61,440  =  231.       =  58,328.886  =  3,785.44 

I  =    16  =     128  =    7,680  =    28.875    =    7,291.1107  =  473.18 

1  =       8  =     480  =     1.8047  =     4556944  =  29.57 

I  =        60  =      O.2256  =         56.9618  =  370 

VOLUME  — LIQUID. 


4  gills  =  1  pint. 
2  pints  =  1  quart. 
4  quarts  =  1  gallon. 


Gills.  Pints.  Gallon.  Cub.  In. 
32    =   8    =    1  =231 


TROY  WEIGHT. 

Pound.            Ounces.         Pennyweights.           Grains.  Grams. 

1       =       12      =      240      =      5,760  =  373-24 

1       =        20      =         480  =  31.10 

I       —          24  =  1.56 

191 


192 


horgan's  half-tone 


THE  CONVERSION  OF  FRENCH  (METRIC) 
INTO  ENGLISH  MEASURE. 


1 

cubic 

centimeter 

= 

17 

minims. 

2 

cubic 

centimeters 

= 

34 

minims. 

3 

cubic 

centimeters 

51 

minims. 

4 

cubic 

centimeters 

= 

68 

minims 

or 

1 

dram 

8 

minims. 

5 

cubic 

centimeters 

= 

85 

minims 

or 

1 

dram 

25 

minims. 

6 

cubic 

centimeters 

= 

101 

minims 

or 

1 

dram 

41 

minims. 

7 

cubic 

centimeters 

= 

118 

minims 

or 

1 

dram 

58 

minims. 

8 

cubic 

centimeters 

= 

135 

minims 

or 

2 

drams 

15 

minims. 

9 

cubic 

centimeters 

152 

minims 

or 

2 

drams 

32 

minims. 

10 

cubic 

centimeters 

= 

169 

minims 

or 

2 

drams 

49 

minims. 

20 

cubic 

centimeters 

338 

minims 

or 

5 

drams 

38 

minims. 

30 

cubic 

centimeters 

507 

minims 

or 

1 

ounce 

0 

dram  27  minims 

40 

cubic 

centimeters 

676 

minims 

or 

1 

ounce 

3 

drams  16  minims 

50 

cubic 

centimeters 

845 

minims 

or 

1 

ounce 

6 

drams  5  minims 

60 

cubic 

centimeters 

1014 

minims 

or 

2 

ounces 

0 

dram  54  minims 

70 

cubic 

centimeters 

1183 

minims 

or 

2 

ounces 

3 

drams  43  minims 

80 

cubic 

centimeters 

1352 

minims 

or 

2 

ounces 

6 

drams  32  minims 

90 

cubic 

centimeters 

1521 

minims 

or 

3 

ounces 

1 

dram  21  minims 

100 

cubic 

centimeters 

1690 

minims 

or 

3 

ounces 

4 

drams  10  minims 

1000 

cubic 

centimeters 

1  liter  =  34  fluid 

ounces 

nearly,  or  2%  pints 

THE  CONVERSION  OF  FRENCH  (METRIC) 


INTO 

ENGLISH  WEIGHT. 

1 

gram 

15f 

grains. 

2 

grams 

30| 

grains. 

3 

grams 

m 

grains. 

dram 

4 

grams 

61| 

grains  

.  .  or 

1 

U 

grains. 

5 

grams 

m 

grains  

... .or 

1 

dram 

17! 

grains. 

6 

grams 

92f 

1 

dram 

32! 

grains. 

7 

grams 

108 

1 

dram 

48 

grains. 

8 

grams 

123f 

grains  

.  ,  .or 

2 

drams 

3! 

grains. 

9 

grams 

138| 

grains  

, . , .or 

2 

drams 

18* 

grains. 

10 

grams 

154! 

grains  

or 

2 

drams 

34! 

grains. 

11 

grams 

169| 

2 

drams 

49| 

grains. 

12 

grams 

185! 

grains  

.  .or 

3 

drams 

5! 

grains. 

13 

grams 

200| 

grains  

.  ,  .or 

3 

drams 

20! 

grains. 

14 

grams 

216 

3 

drams 

36 

grains. 

15 

grams 

231! 

3 

drams 

51! 

grains. 

16 

grams 

247 

4 

drams 

7 

grains. 

17 

grams 

262! 

grains  

or 

4 

drams 

22! 

grains. 

18 

grams 

277| 

grains  

. . . .or 

4 

drams 

37f 

grains. 

19 

grams 

293! 

grains  

or 

4 

drams 

53! 

grains. 

20 

grams 

308| 

5 

drams 

8! 

grains. 

30 

grams 

463 

7 

drams 

43 

grains. 

40 

grams 

617| 

grains  

.  .  .or 

10 

drams 

17! 

grains. 

50 

grams 

771! 

12 

drams 

51! 

grains. 

60 

grams 

926 

15 

drams 

26 

grains. 

70 

grams 

1080! 

18 

drams 

0! 

grains. 

80 

grams 

1234f 

grains  

or 

20 

drams 

34! 

grains. 

90 

grams 

1389 

23 

drams 

9 

grains. 

100 

grams 

1543! 

grains  

,  or 

25 

drams 

43! 

grains. 

1000 

grams 

1  kilogram  =  32  oz., 

1  dr.,  m 

1  gr. 

TABLES 


193 


TABLE  SHOWING  THE  COMPARISON  OF 
THE  READINGS  OF  THERMOMETERS. 


x1  anreniieii; 

Celcius 
Centigrade 

pan  Tnn  t* 
ItCdUmlU 

X1  dill  CJJ.11  tut 

Celcius 
Centigrade 

J-tCclUlild 

—22.0 

—30 

—24.0 

73.4 

23 

18.4 

—13.0 

—25 

—20.0 

75.2 

24 

19.2 

—  4.0 

—20 

—16.0 

77.0 

25 

20.0 

+  5.0 

—15 

—12.0 

78.8 

26 

20.8 

14.0 

—10 

—  8.0 

80.6 

27 

21.6 

23.0 

—  5 

—  4.0 

82.4 

28 

22.4 

24.8 

—  4 

—  3.2 

84.2 

29 

23.2 

26.6 

—  3 

—  2.4 

86.0 

30 

24.0 

28.4 

—  2 

—  1.6 

87.8 

31 

24.8 

30.2 

—  1 

—  0.8 

89.6 

32 

25.6 

91.4 

33 

26.4 

Freezi 

ng  point  of 

water. 

93.2 

34 

27.2 

95.0 

35 

28.0 

32.0 

0 

0.0 

96.8 

36 

28.8 

33.8 

1 

0.8 

98.6 

37 

29.6 

35.6 

2 

1.6 

100.4 

38 

30.4 

37.4 

3 

2.4 

102.2 

39 

31.2 

39.2 

4 

3.2 

104.0 

40 

32.0 

41.0 

5 

4.0 

105.8 

41 

32.8 

42.8 

6 

4.8 

107.6 

42 

33.6 

44.6 

7 

5.6 

109.4 

43 

34.4 

46.4 

8 

6.4 

111.2 

44 

35.2 

48.2 

9 

7.2 

113.0 

45 

36.0 

50.0 

10 

8.0 

122.0 

50 

40.0 

51.8 

11 

8.8 

131.0 

55 

44.0 

53.6 

12 

9.6 

140.0 

60 

48.0 

55.4 

13 

10.4 

149.0 

65 

52.0 

57.2 

14 

11.2 

158.0 

70 

56.0 

59.0 

15 

12.0 

167.0 

75 

60.0 

CO. 8 

16 

12.8 

176.0 

80 

64.0 

62.6 

17 

13.6 

185.0 

85 

68.0 

64.4 

18 

14.4 

194.0 

90 

72.0 

66.2 

19 

15.2 

203.0 

95 

76.0 

68.0 

20 

16.0 

212.0 

100 

80.0 

69.8 

21 

16.8 

71.6 

22 

17.6 

Boili 

ng  point  of 

water. 

13 


POISONS,  SYMPTOMS  AND  ANTIDOTES. 


Many  of  the  chemicals  used  in  processwork  are  poisonous,  either 
when  taken  internally  or  if  absorbed  through  cuts  or  abrasions  in 
the  skin.  In  every  suspicious  case  of  poisoning  a  medical  man  should 
be  at  once  sent  for.  But,  pending  his  arrival,  the  following  remedies 
may  be  applied.  No  time  should  be  lost.  Vomiting  should  be 
brought  on  at  once  by  tickling  the  throat  with  a  small  brush  or 
thrusting  the  fingers  down  the  throat  as  far  as  possible.  Three  or 
four  tumblers  of  warm  mustard  water  usually  acts  as  an  emetic. 
If  it  does  not  act  in  fifteen  minutes,  repeat  it : 


POISONS. 

Acetic  acid. 


SYMPTOMS  AND  EFFECTS. 


ANTIDOTES. 


Corrosion  of  windpipe,  pain  Large  draughts  of  soap  and 


in  abdomen,  perhaps  con- 
vulsions, collapse  and 
death. 


water  to  be  taken  at  once. 
Stomach-pump  not  to  be 
used.  Magnesia,  chalk  and 
water,  lime  -  water,  or 
whitewash  and  water. 


Nitric  acid. 
Hydrochloric 

(muriatic)  acid. 
Sulphuric  acid. 
Or  mineral  acids. 


Alcohol. 
Wood  alcohol. 
Denatured  alcohol. 


Hot,  burning  pains  in  the  Mix  at  once  chalk  and  water 


throat  and  stomach,  lips 
burned  and  shriveled,  ex- 
cessive thirst,  drink  in- 
creasing the  pain. 


Drunkenness,  coma,  death. 


or  soap  and  water.  No 
time  must  be  lost.  If  nec- 
essary, scrape  the  lime 
plaster  from  the  walls, 
make  into  a  thin  paste 
and  give  a  wineglassful 
every  two  minutes.  En- 
courage vomiting  by 
drinking  warm  water. 

Stomach-pump  or  emetics; 
mustard  in  water;  keep 
patient  awake  and  on  the 
move  by  pinching,  shak- 
ing and  walking  him 
about. 


Ammonia. 


Burning    sensation    in    the  Vinegar,  freely  diluted  with 


mouth,  chest,  throat  and 
stomach;  lips  and  tongue 
swollen,  suffocation.  In- 
haling ammonia  _w  i  1  1 
cause  violent  irritation  of 
the  larynx. 


water;  acetic  or  any  other 
acid  diluted  with  large 
quantities  of  water;  lemon 
or  orange  juice.  If  un- 
able to  swallow,  inhal- 
ation of  acetic  acid  or 
vinegar  from  saturated 
pocket  handkerchief. 


Benzin. 


Vapor  acts  as  narcotic;  Brandy,  dram  liquor  am- 
noises  in  the  head,  con-  nia  in  glass  of  water,  fre- 
vulsive  tremblings,  diffi-  quently  repeated;  inhal- 
culty  in  breathing.  ation    of   ammonia;  hot 

and  cold  douches. 


Copper  sulphate. 


Ether. 


Metallic  taste,  constriction  Stomach  -  pump,  egg  -  albu- 
in  throat,  griping  pains  men,  milk,  milk  and  eggs, 
in  abdomen,  headache,  or  emetic  —  warm  water 
giddiness,  coma,  death.  and  mustard. 


Stupefaction. 


Loosen  everything  about  the 
chest,  open  doors  and 
windows  for  fresh  air, 
alternate  cold  and  warm 
douches. 


194 


POISONS,  SYMPTOMS  AND  ANTIDOTES 


195 


SYMPTOMS  AND  EFFECTS. 


ANTIDOTES. 


Iodin. 


Lead  nitrate. 
Mercury  bichlorid. 


Bichromate 
potassium  or 
ammonia. 


Cyanid 
potassium. 


Silver  nitrate. 


Potash  caustic. 


Pain  and  heat  in  throat  and  Stomach  -  pump,     emetic  — 
stomach,    with    vomiting,      mustard  and  water,  egg, 
giddiness,        convulsions,     albumen  and  water, 
death. 

Cramps,  cold  sweat,  convul-  Stomach  -  pump,    emetic  of 
sions.  mustard  and  water. 

Three  grains  fatal  dose.  Whites  of  six  or  eight  eggs 
Burning  in  the  throat  and  beaten  up  in  ten  ounces 
stomach,  nausea,  lips  and  of  water;  give  wineglass- 
mouth  white  and  swollen,  ful  every  two  minutes,  or 
feeble  pulse  and  cold  skin.  milk  and  barley  water,  to 
ease  the  vomiting. 

Powerful     poison.      Acute  Stomach  -  pump    or  emetic, 
pains  in  abdomen,  violent     carbonate  of  magnesia,  or 
vomiting,  pupils  dilated.        chalk  in  milk,  white  of 
egg    in    milk    or  water, 
warmth  to  extremities  and 
give  stimulants  freely. 

Three  grains  fatal.  Violent  Stomach  -  pump  or  emetic, 
poison.  Produces  burning  large  drinks  of  sulphate 
pain  in  stomach,  foaming  of  iron  and  water  at  once, 
at  the  mouth*  insensibil-  ammonia  or  smelling-salts, 
ity,  convulsions,  stiffness  inhalation  of  ammonia, 
of  jaws  and  body,  death. 

Powerful  irritant.    Contrac-  Copious  drinks  of  common 

tion  of  throat  sometimes,  salt  and  water,  white  of 

while  flaky  matter  vomited  egg,  emetic  of  mustard, 
turns  black  on  exposure 
to  air. 

Heat   and   burning  in   the  Give  copious  drinks  of  water 

throat,  extending  to   the  containing  vinegar,  acetic 

stomach.  acid,  citric  acid,  or  lemon 
or  orange  juice. 


LIST  OF  CHEMICALS  USED  IN  PROCESS- 
WORK,  WITH  ENGLISH,  LATIN,  GER- 
MAN AND  FRENCH  NAMES. 


Acid,  acetic 

Acid,  acetic,  glacial 

Acid,  chromic 

Acid,  citric 

Acid,  hydrochloric 

(muriatic) 
Acid,  nitric 

Acid,  pyrogallic, 

pyrogallol 
Acid,  tartaric 
Acid,  sulphuric 

Acid,  tannic, 

tannin 
Alcohol,  ethyl 
Alcohol,  wood 

Alum,  chrome 

Alum,  potassa 

Ammonium 

bichromate 
Ammonium,  iodid 
Benzin 
Benzol 

Cadmium,  bromid 

Cadmium,  iodid 

Collodion 
Copper,  metal 
Copper,  sulphate 
Dextrin 

Ether  (sulphuric) 

Gelatin 
Glycerin 
Glycin 
Gum  arabic 
Gum  sandarac 
Gum  shellac 
Hydrochinon 
Iodin 

Iron  (metal) 


Acidum  aceticum 
Acidum  aceticum 

glaciale 
Acidum  chromicum 
Acidum  citricum 
Acidum  hydro- 

chloricum 
Acidum  nitricum 


Essigsaure 
Eisessig 

Chromsaure 

Citronensaure 

Salzsaure 

Salpetersaure 


Acidum  pyrogal-  Pyrogallussaure, 

licum  Pyrogallol 

Acidum  tartaricum  Weinsteinsaure 

Acidum  sulphur-  Schwefelsaure 
icum 

Acidum  tannicum 


Alcohol 

Alcohol  methyl- 

icum 
Chromii  et  potassi 

sulphas 
Aluminii  et  potassi 

sulphas 
Ammonii  bichrom- 

icum 
Ammonii  iodidum 
Benzinum 
Benzolum 
Cadmii  bromidum 

Cadmii  iodidum 

Collodium 
Cuprum 
Cupri  sulphas 
Dextrinum 
Aether  (sulphur- 

icus) 
Gelatina 
Glycerinum 
Glycinum 
Gummiarabicum 
Sandarac 
Ressina  lacca 
Hydrochinonum 
Iodum,  iodidium 
Ferrum 


Gerbsaure 

Weingeist 
Holzgeist 

Chrom-alaun 

Kali-alaun 

Doppeltchromsaures 

ammon 
Ammoniumiodid 
Petroleumbenzin 
Benzol 

Kadmium  bromid, 
bromkadmium 

Kadmiumjodid, 
jodkadmium 

Collodion 

Kupfer 

Kupfersulfat 

Starkegummi 

Aether, 

schwefelather 

Gelatin 

Glycerin 

Glycin 

Arabisches  gummi 
Sandarak 
Lack  gummilack 
Hydrochinon 
Jod 
Eisen 

196 


Acide  acetique 
Vinaigre  glacial 

Acide  Chromique 
Acide  citrique 
Acide  chlorhydrique 

Acide  nitrique 

(azotique) 
Acide  pyrogallique 

Acide  tartarique 
Acide  sulfurique 

Acide  tannique 

Alcool 

Alcool  methylique 

Alun  chromi- 

potassique 
Sulfate  d'alumine 

et  de  potasse 
Bichromate 

d'ammoniaque 
Iodure  d'ammonium 
Benzine 
Benzole 
Bromure  de 

cadmium 
Iodure  de  cadmium 

Collodion 
Cuivre 

Sulfate  de  cuivre 

Dextrine 

Ether  sulfurique 

Gelatine 

Glycerine 

Glycine 

Gomme  arabique 

Sandaraque 

Laque 

Hydrochinon 

lode 

Fer 


l_-  xl  £.  AL 1  L--r\L«c3 

1Q7 

ENGLISH. 

LATIN. 

GERMAN. 

FRENCH. 

Iron,  chlorid 

Ferro  chloridum 

Eisenchlortir 

Chlorure  de  fer 

(ferrous)  (.fcrro 

(ferro  chlorid) 

(Chlorure 

chlorid) 

f  erreux) 

Iron,  chlorid. 

Ferri  chloridum 

Eisenchlorid 

Perchlorure  de  fer 

(ferric)  (ferric 

(  Fcrri'ScsQuichlori 

(ferrichlorid) 

chlorid) 

dum) 

Iron,  sulphate 

Ferri  sulphas 

Ferrosulfat 

Sulfate  de  fer 

Lead  (metal) 

Plumbum 

Blei 

Plomb 

Lead  nitrate 

Plumbi  nitras 

Bieinitrat 

Nitrate  de  plomb 

Mercury  bichlorid 

Hydrargyri 

Aetzendes  queck- 

Deutochlorure  de 

bichloridum 

silber-chlorid 

mercure 

Oil  of  lavender 

Oleum  lavandulae 

Lavendelol 

Essence  de  lavand 

Oil  of  turpentine 

Oleum  terbinthinae 

Terpintinol 

Essence  terbinthine 

Potassium  bichro- 

Potassii bichromas 

Kaliumbichromat 

Bichromate  de 

mate 

potasse 

Potassium  cyanid 

Potassii  cyanidum 

Cyankalium 

Cyanure  de 

potassium 

Potassium  (caustic 

potash) 

Potassii  hydras  5 

Aetzkali 

Potasse  caustique 

hydrate  potassa 

potassa 

Potassium  iodid 

Potassii  iodidum 

Jodkalium 

Iodure  de  potassium 

Potassium  perman- 

Potassii perman- 

Kaliumperman- 

Permanganate  de 

ganate 

ganas 

ganate 

potasse 

Pyroxylin,  gun- 

Pyroxylinum 

Collodionwolle, 

Pyroxyle,  fulmi- 

cotton 

schiess-baumwolle 

coton 

Silver 

Argentum 

Silber 

Argent 

Silver  chlorid 

Argenti  chloridum 

Silberchlorid 

Chlorure  d'argent 

Silver  iodid 

Argenti  iodidum 

Silberiodid 

Iodure  d'argent 

Silver  nitrate 

Argentinitras 

Silbernitrat 

Nitrate  d'argent 

Sodium  bicarbonate 

Sodii  bicarbonas 

Natriumbicarbonat 

Bicarbonate  de 

soude 

Sodium  carbonate 

Sodii  carbonas 

Natriumcarbonat 

Carbonate  de 

soude 

Sodium  hyposul- 

Sodii  hyposulphis 

Unterschweflig- 

Hyposulfite  de 

phit  or 

saures  natron 

soude 

thiosulphate 

Starch 

Amylum 

Starke  stadkmehl 

Amidon 

Strontium  chlorid 

Strontii  chlordum 

Chlorstrontium 

Chlorure  de 

strontium 

Turpentine,  crude 

Terebinthina 

Geweiner  terpentin 

Terebenthine 

or  white 

communis 

commune 

Water,  distilled 

Aqua  destillata 

Destillirtes-wasser 

Eau  distillee 

Water  of  ammonia 

Aqua  ammonia? 

Salmiakgeist, 

Eau  d'ammoniaque 

ammoniak- 

flussigkeit 

198 


horgan's  half-tone 


TABLE  OF  SYMBOLS  OF  THE  PRINCIPAL 
CHEMICALS  USED  IN  PROCESSWORK. 


Name. 

DTMBOL. 

C2H4O2. 

HC1+7H20. 

HN03. 

H2S04. 

Alcohol,  Ethyl  

C2H60. 

Alcohol,  Methyl  (Wood  Alcohol)  

CH4O. 

Alum  (Potassium  Aluminum  Sulphate)  

A12(S04)3K2S04+24H20. 

Alum  Chrome  (Potassium  Chromic  Sulphate) . 

Cr2(S04)3K2S04-f-24H50. 

NH3 

(NH4)2Cr207. 

NH4Br. 

NH4I. 

Benzol  or  Benzin  (Trioxy-triphenyl-Carbinol) . 

CeHg. 

CdBr2+4H20. 

CDI2. 

Caustic  Potash  (Potassium  Hydrate) 

KOH 

Caustic  Soda  (Sodium  Hydrate)  

NaHO. 

CuS045H20. 

Unobtainable. 

Glycerin  

C3Hg03. 

C8H903N. 

Gold,  Neutral  Chlorid  

AuCl3. 

Ci2H1606(N03)4. 

C,oH1707(NOe)3. 

Hydrochinon  

CeH602. 

NH3OHCl. 

I. 

Iron  Sulphate  (Ferric)  

Fe2(S04)3+9H20. 

Iron  Sulphate  (Ferrous)  

FeS04+7H20. 

Lead  Nitrate  

Pb(N03)2. 

Mercury,  Chlorid  (Mercuric)  (Corros.  Subl.) . . 

HgCl2. 

Mercury  Chlorid  (Mercurous)  (Calomel) 

Hg2Cl. 

Potassium,  Bichromate  

K2Cr267. 

Potassium,  Cyanid  

KCy  or  (CN). 

Potassium,  Ferricyanid  (Red  Prussiate)  

K3FeCy6. 

Potassium,  Ferrocyanid  (Yellow  Prussiate)  — 

K4FeCyfl+3H20. 

KI. 

Silver,  Bromid  

AgBr. 

Silver,  Chlorid  

AgCl. 

Silver,  Iodid  

Agl. 

AgNO,. 

Silver,  Oxid  

Ag20. 

Water  

H20. 

Zinc,  Nitrate  

Zn(N03)26H20. 

SOLUBILITIES  OF  THE  PRINCIPAL  CHEMI- 
CALS USED  IN  PROCESSWORK. 


Abbreviations. —  s.  soluble;  v.s.,  very  soluble;  sp.s.,  sparingly  soluble; 
n.s.,  not  soluble;  dec,  decomposed;  del.,  deliquescent;  in  all  pro.,  in  all 
proportions. 


Name. 

i  part  is 
ible  in 
[  water. 

>  part  is 
ible  in 
water. 

Alcohol. 

o  S  8 

!  Ont 
soli 
hot 

s.  in  a 

11  pro. 
s. 

n.  s. 

s. 

8. 

s.  in  a 

11  pro. 

n.  s. 

A  #»ifi    Snii  1  T"*h  n  pi 

s.  in  a 

11  pro. 

n.  s. 

s.  in  a 

11  pro. 

Alonhnl  TVTpthvl  fWnnrl  AlrnhrkH 

s.  in  a 

11  pro. 

n.  s. 

Alum   1  PAtocoinm    A  1 1 1  TV*  l  m  i  Yn  SliiiT^ri  ata  1 

10 

8 

n.  s. 

Alum  f^riivimp  ( "PrkTQQcinm  f!  Virvimip  £JnlnViQ"f p  l 
ill  1X1  V>X11U111C  \X  UvttDCMUIIl  V^lllvlUlL  O Uipilcl )  . 

10 

dec. 

n.  s. 

very  s 

oluble 

A  tyi tyi t\T\ n i tyi  KipnrAnrtQfo 

v.  s. 

v.  s. 

A  mmnrtinTin  r^YrvmiH 

1.29 

0.7 

qi  c'  * 

O  L  .  O 

A  mm  ati in m   Tnrl i H 

1 

0.5 

s. 

Benzol  or  Benzin  (Tnoxy-tripheny-Carbmol)  . 

n.  s. 

n.  s. 

s. 

l!fiHmiiim  RTvimirl 

1.5 

1 

Sp.  8. 
8. 

1.5 

1 

.5 

.25 

8p.  8. 

I"'!  q  1 1  cf  i  r»  fir*r?Q  (Srkrliiirn  TTvHra to  i 

1.5 

.5 

Sp.  8. 

3 

1 

n.  8. 

sp.  s. 

e.  s. 

n.  s. 

s.  in  a 

11  pro. 

Gold  Npntrfsl  Chlorifl 

1 

5 

fllqn  in  pffipr 

■  2.iiTl/»i~kTT/"kY"i   [  Pat ro _n 1 1 ro  +  ij  fTollii Iaoq  1 

n.  s. 

n.  s. 

1        in  othor 
1       111  ctucl 

Guncotton  (Tri-nitrate  Cellulose)  

n.  s. 

n.  s. 

J  alcohol. 

Hydroxylamin  Hydroclilorate 

0.6 

e.  s. 

4 

Iodin 

sp.  s. 

sp.  s. 

e.  s. 

Iron  Sulphate  (Ferric)  

s. 

dec. 

s. 

Tron  Snlnhatp  (Fprroiis'l 

1.5 

1 

n.  s. 

Lead  Nitrate 

7.7 

7 

s. 

Mercury,  Chlorid  (Mercuric)  (Corros.  Subl.) .  . 

19 

3 

5 

f-^/"\  "f  Q  00111  ty-|       T^l  Ow\  Yf\TY\  O  f  A 

7 

n.  s. 

"f  q  Q  0.111  TYI     f]\m  run 

1 

.5 

sp.  s. 

Pr\tflGCllliT>      Tld  1*1*1  f*\7f\  Tl  1  ri    1  KOn    PfllCGTi  fo  1 

2.5 

1.2 

n.  s. 

Potassium,  Ferrocyanid  (Yellow  Prussiate) .... 

3 

1 

n.  s. 

.75 

.5 

1  in  16 

n.  s. 

n.  s. 

fin  HC1  and 
i  HBr. 

[  ammonia. 

Silver,  Chlorid  

n.  s. 

n.  s. 

1  cyan,  potass 
j  hyposulphit 

{    of  soda. 

n.  s. 

n.  s. 

{    same  as 
\  chlorid. 

1 

.5 

sp.  8. 

Silver,  Oxid  

n.  s. 

n.  s. 

n.  s. 

Zinc,  Nitrate  

del. 

del. 

del. 

199 


TABLE  SHOWING  HOW  PERIOD  OF 
EXPOSURE 

IS  AFFECTED 

BY  THE  CAMERA  EXTENSION  AND  BY  STOP  APERTURE. 


This  table,  taken  from  "  Penrose's  Year  Book  "  for  1896, 
teaches  how  the  period  of  exposure  must  increase  with  the 
distance  of  the  ground  glass  from  the  stop  aperture,  and  as 
the  size  of  the  aperture  in  the  diaphragm  increases  the  time 
of  exposure  must  be  lessened. 


Focus. 

I  In. 

ts  In. 

|  In. 

t  In. 

!  In. 

f  In. 

f  In. 

I  In. 

1  In. 

10 

67 

30 

17 

7| 

4 

3 

2 

1! 

1 

11 

81 

36 

20 

9 

5 

3| 

21 

n 

H 

12 

96 

43 

24 

10| 

6 

4 

2| 

2 

l! 

13 

113 

50 

.28 

12| 

7 

4! 

3 

21 

if 

14 

131 

58 

33 

14! 

8 

5| 

3! 

2! 

2 

15 

150 

66 

38 

16| 

9! 

6 

4| 

3 

2! 

16 

171 

76 

43 

19 

10-1 

6! 

4f 

3! 

2| 

17 

193 

86 

48 

21! 

12 

n 

51 

4 

3 

18 

216 

96 

54 

24 

13! 

8! 

6 

4! 

3| 

19 

241 

107 

60 

27 

15 

61 

5 

3| 

20 

267 

119 

67 

30 

16! 

10! 

7! 

5! 

4 

22 

323 

143 

81 

36 

20 

13 

9 

6! 

5 

24 

384 

171 

96 

43 

24 

15! 

io| 

n 

6 

26 

451 

200 

113 

50 

28 

18 

12! 

n 

7 

28 

523 

232 

131 

58 

32! 

21 

14! 

10f 

8* 

30 

600 

267 

150 

67 

37! 

24 

16 

m 

9! 

32 

683 

303 

171 

76 

42! 

27| 

19 

14 

10! 

34 

771 

343 

193 

86 

48 

31 

21| 

151 

12 

36 

864 

384 

216 

96 

54 

34! 

24 

17! 

13! 

38 

963 

428 

241 

107 

60 

38! 

26| 

19f 

15 

40 

474 

267 

119 

67 

42! 

29f 

21| 

16| 

42 

523 

294 

131 

74 

47 

32! 

24 

18! 

44 

574 

323 

143 

81 

52 

36 

26! 

20 

46 

627 

352 

157 

88 

56 

39 

28f 

22 

48 

683 

384 

171 

96 

62 

43 

31! 

24 

50 

741 

417 

185 

104 

67 

46 

34 

26 

The  numbers  in  the  first  left-hand  column  are  the  dis- 
tances in  inches  from  the  stop  to  the  ground  glass.  The 
fractions  up  to  1  inch,  on  the  top  line,  are  the  diameters  of 
the  opening  in  the  stop.  The  remaining  numbers  in  the  table 
are  the  comparative  periods  of  exposure  required  in  seconds. 


200 


THE  PROGESSWORKERS,  GLOSSARY. 


AN  ENDEAVOR 

TO  STANDARDIZE  MOST  OF  THE  TERMS  COMMONLY 
USED  IN  A  NEW  AND  CONSTANTLY  CHANGING 
BUSINESS. 

BY  S.  H.  H ORGAN. 

ACHROMATIC  — Without  color.    A  lens  which  brings  the  actinic 

and  the  visual  focus  to  the  same  point. 
ACID  —  A  chemical  used  to  corrode  or  etch  metal  plates. 
ACROGRAPHY  —  Engraving  in  a  chalk  coating  on  metal  or  stone. 
ACTINIC  —  The  property  in  light  which  produces  chemical  changes. 
ACTINOMETER  —  Instrument  for  measuring  the  intensity  of  light. 
ACTION  —  Used  to  express  operation  of  light  or  chemicals. 
AEROGRAPH  —  Name  given  to  an  air-brush. 
AFFICHE  —  French  for  poster. 

AIR-BRUSH  —  Atomizer  used  for  the  distribution  of  liquid  color. 
AKROGRAPH  —  Machine  for  producing  engravings,  invented  by 
N.  S.  Amstutz. 

ALBERTYPE  —  Method  of  printing  in  ink  from  gelatin.  A  collo- 
type process  invented  by  Joseph  Albert. 

ALBUMEN  — The  white  of  an  egg.  ALBUMIN  — The  chemical 
term. 

ALGRAPHY  —  Planography,  where  aluminum  plates  are  used 
instead  of  zinc. 

ALKALI  —  That  which  will  neutralize  an  acid.  With  oil  it  forms 
soap. 

AMPHITYPE  —  Process  invented  by  Sir  John  Herschel,  which 
gives  either  a  positive  or  negative. 

ANAGLYPH  —  Stereoscopic  picture  invented  by  Ducos  du  Hauron, 
printed  in  red  and  blue  and  viewed  through  red  and  blue  glasses. 

ANAGLYPTOGRAPH  —  Instrument  for  engraving  medallions  in 
relief  printing-blocks. 

ANASTATIC  —  A  method  of  transferring  printed  matter  after  soft- 
ening the  ink. 

ANASTIGMAT  —  A  lens  corrected  for  astigmatism. 

ANCHORED  —  Plates  secured  to  blocks  by  pouring  molten  metal 
through  holes  bored  through  the  back  of  the  blocks. 

APLANATIC  —  A  lens  corrected  for  spherical  aberration. 

APOCHROMATIC  LENS  — One  corrected  for  chromatic  and 
spherical  aberration.    A  proper  lens  for  colorwork. 

ARGENTOMETER  —  Hydrometer  for  testing  silver  solutions. 

ARTOTYPE  —  A  collotype  process  improved  by  Obernetter. 

201 


202 


horgan's  half-tone 


ASPHALTUM  —  Also  called  asphalt,  bitumen,  bitumen  of  Judea 
and  mineral  pitch.  That  portion  which  dissolves  in  chloroform 
is  most  sensitive  to  light. 

ASSER  PROCESS  —  Early  photolithographic  process  named  after 
the  inventor,  in  which  starch  was  used  instead  of  gelatin. 

ASTIGMATISM  —  A  defect  in  lenses  which  prevents  the  same 
degree  of  sharpness  at  the  edges  of  the  image  as  in  the  center. 
It  is  cured  to  some  extent  by  the  use  of  diaphragms. 

ATOMIZER  —  Instrument  for  spreading  liquids  on  fragile  surfaces. 

AUTOGRAPHIC  PROCESS  — One  in  which  the  writing  or  draw- 
ing becomes  the  printing  surface. 

AUTOTYPOGRAPH Y  —  Any  process  by  which  drawings  can  be 
transferred  direct  to  a  metal  plate  and  impressions  taken. 

BACKGROUND  —  That  portion  of  a  picture  that  can  be  removed 
without  injury  to  the  principal  object. 

BACKING-WOOD  —  A  term  for  the  hard  wood  used  in  blocking 
metal  plates. 

BAKE  —  To  harden  enamel  by  heat  on  metal  plates. 

BATH  —  General  term  given  to  solutions  in  which  plates  or  papers 

are  immersed  or  floated.    Also  for  the  vessel  holding  such 

solution. 

BAUME'  HYDROMETER  — Instrument  for  determining  relative 
densities  of  solutions. 

BEN  DAY  —  Method  of  laying  tints  named  after  the  inventor. 

BICHROMATIZED  GELATIN  —  Gelatin  sensitized  with  a  bichro- 
mate salt. 

BICHROMATIZE  —  To  treat  with  a  bichromate  and  make  sensi- 
tive to  light. 

BITE  —  Submitting  a  metal  plate  to  the  action  of  acid. 
BITUMEN  PROCESS  —  Invented  by  Joseph  Nicephore  Niepce  in 

1813.   The  first  photoengraving  process. 
BLACK-AND-WHITE  —  Common  name  for  pen-and-ink  drawing. 
BLACK  LINE  —  A  style  of  wood  engraving  in  which  the  engraver 

cut  around  the  artist's  lines. 
BLEACHING  OUT  —  Either  removing  color  or  changing  it  to 

white,  as  in  intensification. 
BLOCK  —  Name  given  to  any  type-high  printing  plate. 
BLOCKING  —  Mounting  metal  plates  to  make  them  type-high. 
BLOCKING  GAUGE  — An  instrument  for  keeping  color  plates  in 

register  while  blocking. 
BLOCKING  HAMMER  — Used  in  blocking  plates. 
BLOCKING  NAILS  —  Steel  wire  nails  with  flat  heads  for  securing 

plates  to  their  blocks. 
BLUE-PRINTS  —  Same  as  cyanotype.    Invented  by  Sir  John  Her- 


THE  PROCESSWORKERS'  GLOSSARY 


203 


schell.  Made  of  ferroprussiate  paper  and  named  from  the  color 
of  the  picture. 

BOOK-PLATE  —  Engraved  plate  for  printing  labels  to  denote 
ownership  in  a  book. 

BOXWOOD  —  A  yellowish,  close-grained  wood  used  by  wood- 
engravers. 

BRAYER  — A  small  hand  ink-roller. 

BRISTOL-BOARD  — Cardboard  with  a  hard,  smooth  finish,  used 

for  pen-and-ink  drawings. 
BRUSH  —  An  instrument  for  and  act  of  cleaning  a  plate. 
BUNGED  UP  —  A  shop  expression  for  filled-up  lines  or  dots  in  a 

negative. 

BUR  —  A  rough  edge  of  metal  neglected  by  the  engraver. 
BURIN  —  An  engraver's  tool  with  a  lozenge-shaped  point. 
BURNING-IN  —  Heating  the  enamel  coating  on  a  metal  plate  until 

it  carbonizes  and  becomes  acid-resistant. 
BURNISH  —  Rubbing  on  a  plate  to  make  it  print  darker,  if  a  relief 

plate,  and  lighter,  if  an  intaglio  plate. 
BURNISHER  —  An  instrument  of  tempered  steel  for  polishing  a 

plate. 

CALIPERS  —  A  tool  for  marking  on  the  back  of  a  metal  plate  the 
location  of  defects  on  its  face. 

CALLIGRAPHIC  ETCHING  — A  design  is  made  on  a  metal  plate 
with  an  ink  soluble  in  water.  The  whole  is  covered  with  a  thin 
varnish  of  asphalt,  dragon's-blood  or  shellac,  then  soaked  in  a 
slightly  alkaline  water  until  the  ink  softens  and  can  be  washed 
away,  carrying  the  overlying  varnish.  The  plate  is  then  etched 
intaglio. 

CAMERA  —  The  pattern  of  camera  obscura  used  in  photography. 
CAMERA  LUCIDA  —  An  arrangement  of  a  prism  used  by  artists 

in  copying  objects. 
CAMERA  STAND  —  The  support  for  the  camera  box,  arranged  to 

prevent  vibration. 
CAMERA  SWING  —  A  suspended  camera  stand. 
CARBON  PROCESS  —  Method  of  producing  positives  in  gelatin 

impregnated  with  a  pigment.    Used  in  photogravure  and  rotary 

photogravure. 

CAST  —  Anything  formed  by  pouring,  while  liquid,  into  a  mold,  as 
plaster  into  a  gelatin  mold  or  stereotype  metal  into  a  matrix. 

CASTING-BOX  —  The  apparatus  used  for  casting. 

CEROGRAPH Y  —  Engraving  in  wax.  Used  largely  by  map  engra- 
vers. 

CHALK  PLATE  —  An  engraving  made  with  a  steel  point  through 
a  chalk  coating  on  a  steel  plate.  Afterward  cast  in  stereotype 
metal. 


204 


horgan's  half-tone 


CHALK  ENGRAVING  — An  engraving  made  with  a  steel  point 
through  a  chalk  coating  on  a  metal  plate,  which  is  later  cast  in 
stereotype  metal. 

CHEMIGLYPHIC  — Engraved  by  chemical  action. 

CHEMIGRAPHY  — Relief  etching  on  metal. 

CHEMITYPE  —  A  zinc  plate  etched  first  slightly  intaglio,  the  inci- 
sions filled  in  with  fusible  metal,  after  which  the  zinc  is  etched 
in  relief. 

CHIARAOSCURO  —  A  method  of  printing  engravings  from  several 

blocks  representing  lighter  and  darker  shades. 
CHINA  WHITE  —  A  very  pure  variety  of  white  lead. 
CHINESE  WHITE  —  A  very  pure  white,  made  from  zinc  oxid. 
CHROMATIC  —  Relating  to  color.  Colored. 

CHROMATIC  ABERRATION  —  The  lack  of  color  correction  in 
a  lens. 

CHROMOCOLLOTYPE  — A  collotype  printed  in  colors. 
CHROMOLITHOGRAPHY  — Lithographic  printing  in  colors. 
CHROMOPHOTOGRAPH  —  A  picture  produced  in  colors  by  pho- 
tography. 

CLICHE' — A  French  word  for  negative.  Properly  a  stereotype  or 
electrotype. 

COLLOGEN  or  COLLAGEN  —  A  glue  or  gelatin. 

COLLOID  —  Substances  similar  to  glue,  such  as  gelatin,  dextrin, 
gum,  casein,  starch,  albumen,  caramel,  cellulose  and  tannin. 

COLLOTYPE — (In  German,  Lichtdruck;  French,  Phototypie). 
Known  in  the  United  States  as  Albertype,  Artotype,  Heliotype 
and  Gelatin  Printing.  It  is  a  method  of  printing  in  the  litho- 
graphic manner  from  a  sheet  of  bichromatized  gelatin  that  has 
been  exposed  to  light  under  a  reversed  negative. 

COLOR  FILTER  —  Same  as  Color  Screen.  Any  colored  medium 
by  which  some  colors  are  excluded  when  photographing. 

COLOR  PLATE  —  One  of  a  set  or  series  of  engraved  plates,  which, 
combined  by  printing,  produce  a  picture  in  colors. 

COLOR  SCREEN  — A  color  filter. 

COLOR-SENSITIZING  — The  method  by  which  photographic  sur- 
faces are  rendered  sensitive  to  certain  colors,  or  to  all  colors 
equally. 

COMB  —  A  steel  tool  grooved  to  match  half-tone  screens  and  used 

as  a  multiple  graver. 
COMBINATION  PLATE  — Made  by  stripping  line  and  half-tone 

negative  films  together  in  a  design  on  the  same  glass,  printing 

from  this  combination  negative  and  etching  the  plate. 
COMBINATION  PLATES  FOR  COLOR  PRINTING  — Those 

in  which  a  key-plate  is  used  with  plates  for  two  or  more  colors. 


THE  PROCESSWORKERS'  GLOSSARY 


205 


COMETS  —  Spots  of  dirt  on  a  sensitive  plate,  which  on  development 
take  the  shape  of  comets. 

CONTACT  —  Term  used  when  two  surfaces  are  brought  absolutely- 
together.  When  surfaces  do  not  come  together  it  is  called  "  lack 
of  contact/' 

CONTE  PROCESS  —  A  zinc  plate  is  covered  with  a  gum  and  zinc- 
white  varnish.  The  design  is  etched  through  it  with  stylus-like 
points.  The  whole  is  inked  up  with  greasy  ink  and  soaked  in 
water,  when  the  gum  varnish  comes  away,  leaving  the  design 
in  greasy  ink,  which  can  be  either  etched  in  relief  or  printed  from 
planographically. 

CONTINUING  ACTION  OF  LIGHT  — Name  given  to  the  action 
that  goes  on  in  bichromatized  gelatin  after  it  has  been  exposed 
to  light. 

CONTRAST  —  A  requisite  in  negatives  for  photomechanical  proc- 
esses where  the  final  result  is  to  be  in  black-and-white. 

CONTRASTY  —  Term  applied  to  negatives  or  proofs  where  the 
shadows  and  high  lights  are  strongly  indicated. 

COPPER  ETCHING  — A  design  in  lines  etched  on  copper. 

COPPERPLATE  ENGRAVING— Intaglio  engraving,  also  called 
line  engraving.  The  lines  in  the  plate  are  incised  either  with  a 
burin  or  corroded  with  an  etching  solution. 

COPY  —  Any  subject,  whether  drawing,  painting  or  object,  sub- 
mitted for  photomechanical  reproduction. 

COPY-BOARD  — The  board  to  which  copy  is  affixed  for  photo- 
graphing. 

COPYHOLDER  — A  sheet  of  plate  glass  framed,  with  a  back  board, 
between  which  and  the  glass,  copy  can  be  held  flat  while  copying. 

COPYING  CAMERA  —  Name  given  to  the  camera  used  by  process- 
workers. 

COTTON  —  An  abbreviation  for  guncotton  or  pyroxylin. 
C.  P. —  Chemically  pure. 

CRAPE  MARKINGS  —  A  defect  in  collodion  which  shows  itself  in 
the  wet  process  and  in  collodion  emulsion.  Named  from  its 
resemblance  to  crape. 

CRAYON  ENGRAVING  —  The  imitation  of  crayon  drawing  by  an 
intaglio  plate,  the  engraving  being  done  with  roulettes,  points 
and  multiple  punches. 

CROP  —  When  marked  on  copy  means  that  the  plate  is  to  be  cut 
off  at  the  line  marked  near  the  word  "  crop." 

CUT  —  An  abbreviation  of  woodcut,  not  applicable  to  photoengra- 
vings, though  used  for  the  engravings  on  newspapers. 

CUT-OUT  —  Name  given  to  a  high-light  process  in  which  a  nega- 
tive without  a  screen  is  used  over  the  glass  in  the  printing  frame 


206 


horgan's  half-tone 


to  mask  or  cut  out  the  high  lights  in  the  half-tone  negative  in 
the  frame. 

CUTTING  —  The  dissolving  away  of  the  fringe  of  deposit  left  by 

the  developer  around  the  dots  in  half-tone  negatives. 
CYANOTYPE  — -  Name  given  by  Sir  John  Herschel  to  blue-print 

process  which  he  invented. 
DAGUERROTYPE  —  First  perfected  photographic  process,  given 

free  to  the  world  January  7,  1839.   The  photographic  image  was 

made  on  a  silver-plated  copper  mirror. 
DARKROOM  —  Where  the  operations  of  handling  material  sensitive 

to  light  is  carried  on.    It  can  be  well  illuminated  providing  the 

light  used  is  nonactinic. 
DARK  SLIDE  —  The  English  term  for  plateholder. 
DEEP  ETCHING  —  Where  additional  etching  is  required. 
DEFINITION  —  In  a  lens  is  the  property  of  giving  a  sharp  image 

on  the  ground  glass. 
DENSITY  —  In  photographic  language  signifies  opacity. 
DESENSITIZE  —  Giving  stone  or  metal  surfaces  a  grease-resisting 

treatment. 

DETAIL  —  A  minute  part  of  a  negative,  picture  or  print. 
DEVELOPER  —  The  agent  which  renders  visible  the  invisible 
image. 

DEVELOPMENT  —  The  production  of  a  visible  image  from  an 

invisible  or  latent  one. 
DEVILS  —  Holes   which   appear   in   photogravure  plates  during 

etching. 

DIAPHRAGM  —  Or  stop,  used  in  a  lens  to  increase  definition.  In 

half-tone  it  is  used  to  control  the  size  and  shape  of  the  dots. 
DIAPOSITIVE  —  A  positive  made  from  a  negative. 
DIP  —  Each  intensification  of  a  negative  is  a  dip. 
DIPPER  —  The  holder  for  the  collodionized  glass  plate,  by  which 

it  is  lowered  and  raised  from  the  silver  bath. 
DIRECT  HALF-TONE  — When  the  half-tone  negative  is  made 

direct  from  an  object  and  not  from  a  drawing  or  photograph 

of  it. 

DIRECT  PROCESS  — In  color-plate  making,  when  the  half-tone 
negatives  are  made  direct  through  color  screens. 

DISTORTION  —  In  an  image  may  come  from  the  lens,  lack  of 
parallelism  between  ground  glass  and  copy,  in  stripping  the 
negative  film,  or  the  carbon  film  in  photogravure. 

DRAGON'S-BLOOD  — A  red  resin,  supposed  to  exude  from  the 
fruit  of  the  Calamus  Draco,  a  rattan  palm  found  in  Malay. 

DUOGRAPH  —  Two  half-tone  plates  made  from  the  same  copy  at 
different  screen  angles  and  printed  in  two  shades  of  the  same 
color  or  a  strong  color  and  a  tint. 


THE  PROCESSWORKERS'  GLOSSARY 


207 


DUOTYPE  —  Two  half-tone  plates  made  from  the  same  negative, 
but  etched  differently. 

DUST  GRAIN  —  An  acid-resisting  grain  produced  on  a  metal  plate 
by  allowing  powdered  resin  to  fall  upon  it. 

DUSTING-BOX  —  The  apparatus  used  in  producing  a  dust  grain. 

DUTCH  MORDANT  —  Etching  solution  for  copper  in  which  chlo- 
rate of  potash  and  hydrochloric  acid  are  used. 

ELECTRO  —  Abbreviation  of  electrotype.    An  electrotype. 

ELECTROENGRAVING  — Etching  a  metal  plate  by  galvanic 
action. 

ELECTROGRAPH  —  Apparatus  used  in  engraving  mechanically 
copper  cylinders  for  fabric  or  wall-paper  printing. 

ELECTROSTEELING  —  Electroplating  engraved  copper  plates 
with  iron  to  withstand  wear  in  printing. 

ELECTROTINTING  —  A  design  is  put  on  a  metal  plate  in  an 
acid-resisting  varnish,  when  it  is  placed  in  an  electric  bath  and 
etched  in  relief  by  galvanic  action.  Electroengraving. 

ELECTROTYPE  —  A  duplicate  in  metal  of  an  engraved  or  molded 
surface  made  by  galvanic  action  and  backed  up  with  type  metal. 

ELECTROTYPE  SHELL  —  The  thin  metal  duplicate  made  by  gal- 
vanic action  before  it  is  backed  up  with  type  metal. 

EM  —  The  square  of  the  body  of  any  size  of  type. 

EMBOSSING-PLATE  — A  plate  engraved  or  etched  for  the  pur- 
pose of  producing  figures  or  designs  in  relief. 

EMULSION- — Gelatin  or  collodion  holding  minutely  divided  silver 
salts  in  suspension. 

ENAMEL  —  A  coating,  on  a  metal  plate,  of  sensitized  glue,  albu- 
men, gum,  or  a  mixture  of  them,  on  which  a  photographic  image 
is  produced.  This  is  carbonized  by  heat  and  becomes  a  strong 
acid  resist. 

ENAMEL  PRINT  —  An  image  produced  on  enamel  by  photography. 

ENCLOSED  ARC  —  An  electric  arc  lamp  in  which  the  light  burns 
in  a  partial  vacuum,  producing  violet  rays. 

ENGRAVE  —  To  cut,  incise  or  etch  in  a  surface,  especially  for  print- 
ing purposes. 

ENGRAVED  HALF-TONE  — A  half-tone  that  has  been  gone  over 
with  a  burin  in  the  hands  of  an  engraver. 

ENGRAVER  —  One  who  represents  objects  by  incisions  in  a  sur- 
face, either  by  hand,  mechanically  or  photographically,  from 
which  impressions  may  be  taken  in  printing-ink. 

ENGRAVER'S  METAL  —  An  alloy  similar  to  type  metal,  on  which 
engravings  or  tints  can  be  produced. 

ENGRAVER'S  PAD  — A  leather  sand-bag  on  which  the  engraver 
rests  a  plate  or  block  while  working  on  it. 

ENGRAVER'S  PROOF  — A  carefully  pulled  impression  in  printing- 


208 


horgan's  half-tone 


ink  taken  from  an  engraving  to  show  the  engraver's  work  at 
its  best. 

ENGRAVING  —  The  act  of  producing  designs  on  a  surface,  either 
in  relief  or  intaglio,  for  printing  purposes.  The  plate  or  block 
that  has  been  either  incised  or  engraved  in  relief.  The  impres- 
sion from  an  engraved  plate. 

ENLARGEMENT  —  A  reproduction  of  a  greater  size  than  the  orig- 
inal copy. 

ENLARGING  —  Making  a  larger  image  from  a  negative  or  positive 

on  a  sensitive  surface. 
ENLARGING-CAMERA  —  A    camera    specially   constructed  for 

making  enlargements. 
ETCHED  NEGATIVE  —  A  negative  made  by  drawing  with  a  needle 

point  through  an  opaque  ground  on  a  glass  plate. 
ETCHING  —  The  production  of  an  engraving  by  corrosion  with  an 

acid.    The  plate  produced  by  acid  corrosion.    The  impression 

in  printing-ink  from  an  etched  plate. 
ETCHING-BATH  —  The  acid  solution,  mordant  or  etching  fluid 

used  in  producing  an  etching. 
ETCHING-GROUND  — The  coating  on  a  metal  plate  to  protect  the 

surface  from  the  action  of  the  acid. 
ETCHING-INK  —  An  ink  having  special  acid-resisting  properties. 
ETCHING-MACHINE  — An  apparatus  for  hastening  the  action  of 

the  etching  fluid,  usually  operated  by  power. 
ETCHING-NEEDLE  —  A  sharp  instrument  of  steel  for  drawing 

through  an  etching-ground.    An  etching-point. 
ETCHING-POINT  —  An  etching-needle. 

ETCHING-POWDER  —  An  acid-resisting  resin  in  powder  form. 
ETCHING-ROOM  —  The  place  where  etching  is  done. 
ETCHING  SOLUTION  —  The  fluid  or  mordant  used  in  corroding 
a  metal  plate. 

ETCHING-TUB  — •  A  shallow  acid-proof  box  in  which  metal  plates 

are  rocked  in  the  etching  fluid. 
EVAPORATING-DISH  —  Used  for  boiling  down  the  silver  bath. 
EXPOSURE  —  The  act  of  submitting  a  sensitized  surface  to  the 

action  of  light. 

EXPOSURE  METER  —  An  instrument  for  measuring  the  strength 

of  light  so  as  to  indicate  the  correct  exposure. 
FACSIMILE  —  A  reproduction  the  same  size  and  an  exact  copy  of 

the  original. 

FERROPRUSSIATE  PAPER  — Commonly  called  blue-print  paper. 
FERROTYPE  —  A  positive  photograph  made  on  a  sensitized  sheet 

of  iron.    Commonly  called  tintype. 
FILM  —  Any  thin  skin  of  gelatin,  collodion,  albumen,  varnish  or 

other  liquid  remaining  after  its  solvent  has  evaporated. 


THE  PROCESSWORKERS'  GLOSSARY 


209 


FINE  ETCHING  —  Another  name  for  reetching  or  staging  a  half- 
tone engraving. 

FINE  LINE  —  Term  applied  to  the  most  delicate  line  in  an  engra- 
ving. 

FINISH  —  The  style  of  treatment  given  an  engraving  to  complete  it, 
such  as  "  vignetted,"  "  square,"  "  oval,"  etc. 

FINISHER  —  The  engraver  who  reetches  and  retouches  an  engra- 
ving to  make  it  ready  for  the  final  proof. 

FINISHING-ETCH  — The  last  or  deep  etch  given  a  metal  plate  to 
make  the  incisions  of  sufficient  depth. 

FINISHING-INK  — The  etching-ink  rolled  on  a  plate  before  the 
finishing-etch. 

FISH  GLUE  —  Glue  made  from  fishes  and  used  in  the  enamel  acid 
resist. 

FIXING  —  Term  applied  to  the  dissolving  away  of  the  sensitive 

salt  unacted  upon  by  light. 
FLASHING  —  In  half-tone  negative-making,  the  exposure,  with  a 

small  stop,  of  the  sensitive  plate  for  a  short  period  to  white 

paper. 

FLAT  —  Lack  of  vigor  or  contrast  in  a  negative,  photograph  or 

print  of  any  kind. 
FLAT  —  Term  used  for  a  glass  on  which  several  negative  films  are 

laid  together  to  save  time  in  printing  and  etching.    The  etched 

plate  is  also  called  a  flat. 
FLATNESS  OF  FIELD  — A  quality  in  a  lens  most  desirable  for 

copying  purposes. 
FLAT  PROOF  —  An  impression  taken  from  a  metal  plate  without 

underlay  or  overlay. 
FOCUS  —  A  point  at  which  rays  of  light  meet  again  after  diverging 

from  one  point  and  passing  through  a  lens. 
FOCUSING  —  The  act  of  bringing  an  image  to  a  focus  on  the 

ground  glass  of  a  camera. 
FOCUSING-CLOTH  —  An  opaque  cloth  used  to  cover  the  head 

and  shut  out  unnecessary  light  while  focusing. 
FOCUSING-GLASS  —  A  magnifying  glass  used  on  the  ground 

glass  to  determine  when  the  image  is  in  the  sharpest  focus. 
FOCUSING-SCREEN  —  The  ground  glass  on  which  the  image  is 

brought  to  a  focus. 
FOG  —  Any  veil  or  discoloration  appearing  on  a  negative  during 

development. 

FORMULA  —  A  list  of  the  ingredients  and  their  quantities  that  make 
up  a  solution  or  compound  used  in  processwork. 

FOUR-COLOR  PLATES  —  A  set  of  color  plates  including  a  gray 
or  black  plate. 

14 


210 


horgan's  half-tone 


FOUR-COLOR  PROCESS  — The  method  of  reproducing  objects 
in  color  in  which  four  printing-plates  are  used. 

FOUR- WAY  POWDERING  — Brushing  acid-resisting  powder  in 
four  directions  on  a  plate  to  protect  the  raised  lines  during 
etching. 

FULL-TONE  —  An  engraving  made  through  a  screen  and  contain- 
ing pure  whites  and  solid  blacks  besides  the  half-tones.  A  high- 
light half-tone. 

GELATIN  —  A  substance  which  swells  in  cold  water,  dissolves  in 

warm  water,  and  solidifies  or  jellies  again  when  cold. 
GELATIN  PROCESS  —  An  obsolete  photoengraving  process  in 

which  gelatin  was  sensitized,  exposed  to  light  and  swollen  into 

relief,  known  as  the  swelled-gelatin  process. 
GELATIN  RELIEF  —  An  image  composed  of  gelatin  in  relief. 
GELATOSE  —  A  glue  or  gelatin  that  has  its  swelling  property 

destroyed.    Fish  glue.  Metagelatin. 
GILLOTAGE  —  The  method  of  etching  zinc  in  which  the  plate  is 

rolled  up  with  a  soft  etching-ink  between  bites.    The  ink  is 

melted  and  flows  down  the  sides  of  the  relief  line  to  protect  it 

from  the  etching-fluid. 
GILLOT  PROCESS  —  Invented  in  Paris  in  1859  by  Gillot,  who 

transferred  from  a  litho  stone  to  zinc,  powdered  the  transfer 

with  resin  and  etched  it  into  relief. 
GLUED-UP  BACKING  — Blocking- wood  that  has  been  tongued 

and  grooved  and  cemented  together. 
GOUPIL  PROCESS  —  Used  for  making  color  plates  in  grain,  by 

an  artist,  after  the  image  is  photographed  on  the  metal  plate. 
GRAIN  —  Any  fine  powder  that  produces  a  granular  appearance 

on  either  a  negative  or  printing  plate. 
GRAINED  PLATE  — Any  relief  printing-plate  in  which  the  print- 
ing surface  is  in  a  grain.    Used  chiefly  on  the  offset  press  and 

in  color  printing. 

GRAINING-BATH  —  A  solution  for  producing  a  grain  on  the  sur- 
face of  a  metal  plate  by  chemical  means. 

GRAINING-MACHINE  —  Apparatus  used  to  produce  a  grain  on 
a  metal  plate. 

GRAINING-SAND  —  The  granular  cutting  material  used  in  pro- 
ducing a  grain  on  a  metal  plate  mechanically. 

GRAPHOTYPE  —  Drawings  made  on  a  chalk-covered  plate  in  an 
ink  which  hardens  the  chalk  so  that  the  unhardened  chalk  may 
be  brushed  away  and  the  relief  thus  made  stereotyped  from. 

GRAVER  —  A  tool  used  for  engraving. 

GRAY  —  A  photoengravers'  term  for  any  print  that  is  not  suffi- 
ciently dark.    A  light  impression. 
GUMMING  SOLUTION  —  Composed  of  gum  arabic  chiefly  and 


THE  PROCESSWORKERS'  GLOSSARY 


211 


used  to  prevent  greasy  ink  from  adhering  to  a  metal  plate  or 
litho  stone. 

HALATION  —  In  a  negative  is  a  reflection  of  light  from  the  back 

surface  of  the  negative  glass. 
HALF-TONE  —  A  printing-plate  or  picture  made  by  the  half-tone 

process. 

HALF-TONE,  OUTLINED  — A  half-tone  with  the  background 

outside  of  the  object  entirely  cut  away,  leaving  a  definite  edge 

without  shading  or  vignetting. 
HALF-TONE,  OUTLINED  AND  VIGNETTED  — A  half-tone  in 

which  part  of  the  background  is  cut  away  and  part  vignetted. 
HALF-TONE  PLATEHOLDER  — A  light-tight  box  for  holding 

both  the  sensitive  plate  and  half-tone  screen  and  inserting  them 

in  the  camera. 

HALF-TONE  PROCESS  — A  photomechanical  method  of  making 
printing  surfaces  in  which  the  object  is  photographed  through 
a  grating  called  a  half-tone  screen.  In  German,  it  is  autotypie; 
in  French,  similigravure. 

HALF-TONE  SCREEN  — A  grating  of  opaque  lines,  usually  ruled 
on  glass,  through  which  light  from  the  object  passes  in  photo- 
graphing for  the  half-tone  process. 

HALF-TONE,  SQUARE-PLATE  —  A  half-tone  in  which  the  out- 
side edges  are  rectangular  and  parallel.  May  be  with  or  with- 
out single  black  line  border. 

HAND  PROOF  —  A  carefully  pulled  impression  of  a  printing 
surface. 

HAND  REST  —  A  rest  for  the  hand  while  working  over  a  printing 
surface. 

HAND  TOOLING  —  Any  work  done  by  use  of  a  tool  upon  the 
plate  to  increase  the  contrast  of  the  etched  plate. 

HARDENING  BATH  — Any  solution  that  toughens  a  substance. 
Used  to  harden  gelatin  and  glue  in  processwork. 

HELIOGRAPHY  — The  Greek  for  "sun-drawing,"  and  applied  by 
Niepce  to  the  first  photoengraving  made. 

HELIOGRAVURE  —  A  term  used  in  some  countries  for  "photo- 
engraving." 

HELIOTYPE  —  A  collotype  process  in  which  metal  is  used  instead 
of  glass  to  support  the  gelatin  printing  surface. 

HICKEY  —  A  slang  word  used  by  photoengravers  for  a  slight  defect 
in  a  negative  or  printing-plate.    Named  after  Jim  Hickey. 

HIGH  LIGHT  —  The  brightest  part  of  a  picture.  The  densest  por- 
tion of  a  negative. 

HIGH-LIGHT  HALF-TONE  — A  half-tone  plate  in  which  the 
elimination  of  the  dots  in  the  high  lights  is  accomplished  by  a 
photomechanical  method  instead  of  cutting  them  out  with  a  tool. 


212 


horgan's  half-tone 


HIGH-LIGHT  PROCESS  — A  half-tone  process  in  which  the  high- 
est lights  appear  white  in  the  finished  print. 

HIGH-LIGHT  STOP  —  The  diaphragm  used  to  join  up  the  high 
lights  in  half-tone  negative-making. 

HYDROMETER  —  An  instrument  for  determining  the  densities  of 
liquids. 

IMAGE  —  The  picture  formed  on  the  ground  glass  of  a  camera. 
INDIA  INK  —  An  ink  made  in  China  and  Japan.    Now  applied 

to  black  drawing-ink. 
INDIRECT  PROCESS  —  Term  applied  to  color  plate-making  when 

the  half-tone  negative  is  not  made  directly  through  the  half-tone 

screen  and  color  filter. 
INDOTINT  —  A  collotype  process  in  which  the  gelatin  printing 

film  was  attached  to  a  sand-blasted  copper  plate. 
INKING  IN  —  Drawing  in  ink  over  a  photograph  or  pencil  sketch. 

Sometimes  applied  to  inking  an  intaglio  plate. 
INKING-ROLLER  —  Used  for  applying  a  coating  of  ink  to  any 

surface. 

INKING  UP  —  Term  used  for  coating  any  photographic  surface 

with  ink  after  it  has  been  exposed  to  light. 
INK-PHOTO  —  A  collotype  process  used  in  England. 
INK  SLAB  —  A  stone,  metal  or  glass  surface  on  which  printing- 
ink  is  distributed. 
INSIDE  MORTISE  —  An  opening  cut  entirely  inside  the  printing 

block  for  the  insertion  of  type  or  other  purposes. 
INTAGLIO  —  An  engraving  in  which  the  printing  lines  are  sunken 

instead  of  being  raised. 
INTAGLIO  ETCHING — Sinking  or  incising  the  lines  in  a  plate  by 

the  use  of  a  corrosive  liquid. 
INTAGLIO  PLATE  — A  printing-plate  in  which  the  lines  are 

incised  or  sunken,  either  by  punching,  engraving  with  a  burin, 

or  etching. 

INTAGLIOTYPE  —  Intaglio  engraving  produced  by  drawing  with  a 
special  ink  on  a  plate  coated  with  compressed  zinc  oxid.  When 
the  drawing  is  developed  it  is  stereotyped  or  electrotyped. 

INTENSIFICATION  — The  act  of  increasing  the  opacity  of  a 
developed  image. 

INTENSIFIER  — An  agent  used  to  increase  the  opacity  of  a  devel- 
oped image. 

ISOCHROMATIC  —  Same  as  orthochromatic.  A  method  of  repro- 
ducing colors  in  their  relative  tone  values  as  regards  light  and 
dark. 

ISOTYPIE  —  Name  given  to  half-tones  made  with  diaphragms  hav- 
ing more  than  one  opening. 
JIG  SAW  —  A  reciprocating  saw  used  for  cutting  inside  mortises. 


THE  PROCESSWORKERS'  GLOSSARY 


213 


KEY-PLATE  —  The  outline  plate,  or  the  one  containing  most  of 

the  design  in  color  printing. 
KNURL  —  The  small  wheel  in  a  roulette. 

LAMINATED  BACKING  — Mounting  or  blocking  wood  consisting 
of  layers  of  wood  glued  together,  with  the  grain  crossing  alter- 
nately. 

LATENT  IMAGE  —  The  invisible  picture  on  a  sensitive  surface 
before  development. 

LAYING  DOWN  THE  TRANSFER  — In  lithography  or  piano- 
graph  work,  the  act  of  transferring  to  the  stone  or  metal  plate. 

LAYING-DOWN  TINTS  —  Covering  surfaces  with  lines,  dots  or 
a  grain  by  tint  transfers,  shading-mediums,  spatterwork,  air- 
brush or  resin  dust. 

LEIMTYPE  —  The  original  "wash-out"  gelatin  process.  It  pro- 
duced a  hardened  gelatin  relief  which  was  attached  by  gutta- 
percha to  a  mount  and  used  as  a  printing-block.  Called  "  photo- 
electrotype  "  when  the  electrotype  from  it  was  used  to  print 
from. 

LENS  —  Used  in  photographic  work  is  constructed  to  bring  the 
visual  focus  and  the  actinic  focus  to  the  same  point. 

LEVELING-STAND  —  Arranged  with  screws  to  bring  a  plate  set 
on  it  perfectly  level.  Used  in  getting  a  film  of  gelatin  of  even 
thickness. 

LICHTDRUCK  —  The  German  name  for  collotype. 
LIGHT  FILTER — Same  as  color  screen  or  color  filter. 
LINE  BLOCK  —  Name  given  to  relief  block  in  lines.    A  zinc 
etching. 

LINE  ENGRAVING — 'Intaglio  engraving  executed  on  the  bare 
metal  with  gravers  or  burins.    Usually  in  copper. 

LINE  DRAWING  —  A  drawing  made  with  pen  and  ink. 

LINEHOLDER  —  A  clamp  for  holding  a  small  block  when  trim- 
ming its  sides  on  a  machine. 

LINE  NEGATIVE  —  A  negative  from  a  drawing  or  other  copy  in 
lines  or  stipple. 

LINER  AND  BEVELER  — A  machine  for  beveling  the  edges  of  a 
printing-plate  and  raising  a  black  line  around  the  picture. 

LINING-TOOL  —  An  engraving  tool  with  a  number  of  cutting 
points  to  match  a  half-tone  screen.  Sometimes  called  "multi- 
ple "  tool. 

LINO  CUTS  —  Engravings  on  linoleum  used  in  poster  work. 
LITHOGRAPHY  —  The  art  of  printing  from  stone.    Printing  in  a 

similar  manner  from  metal  surfaces  is  termed  "  planography." 
LITMUS  PAPER  — Used  for  testing  acidity  or  alkalinity.  Acid 

turns  blue  litmus  paper  red,  and  an  alkali  restores  the  red  paper 

to  blue. 


214 


HORGAN  S  HALF-TONE 


MACHINE  ETCHING  — The  modern  method  of  applying  an  etch- 
ing fluid  to  a  metal  plate  instead  of  the  former  "tub"  etching. 

MAKE-READY  —  Preparing  an  engraving  for  proving.  The  sheet 
on  which  the  underlays  are  pasted. 

MALE  DIE  —  The  relief  die  in  a  set  of  embossing  plates. 

MASKING  —  Shading  portions  of  a  negative  during  exposure  to 
light  in  photographic  printing. 

MECHANICAL  DRAWING— Is  made  by  means  of  squares,  rules 
and  compasses. 

MERCUROGRAPHIE  — A  process  based  on  the  fact  that  mercury 
amalgamated  with  the  surface  of  a  zinc  plate  repels  ink. 

METAGELATIN  —  Gelatin  that  has  lost  its  swelling  property. 

METAL  BASE  —  The  type-metal  block  on  which  engraved  plates 
are  mounted  in  place  of  wood. 

METAL  ENGRAVING  —  Is  applied  chiefly  to  engraving  in  type 
metal. 

MEZZOGRAPH  —  A  half-tone  made  by  the  use  of  a  grained  screen 

instead  of  a  cross-line  screen. 
MEZZOGRAPH  SCREEN  — A  transparent  glass  screen  having  a 

reticulated  surface  used  to  get  grain  effects  in  printing  surfaces. 
MEZZOTINT  —  A  method  of  engraving  in  which  the  surface  of 

the  copper  plate  is  first  uniformly  roughened,  and  then  the 

effects  are  produced  by  scraping  away  the  bur,  as  it  is  called, 

and  by  burnishing. 
MINIMUM  —  The  lowest  charge  made  for  engravings.  Usually 

for  blocks  10  square  inches  and  smaller. 
MODELED  PLATE  —  Half-tone  made  from  a  bas-relief  in  clay, 

plaster,  wax,  etc. 

MOIRE  —  The  varied  pattern  obtained  when  reproducing  a  half- 
tone through  a  half-tone  screen.  When  the  screens  are  not  at 
the  proper  angles  in  a  set  of  color  plates  it  also  appears. 

MORDANT  —  Any  corrosive  liquid  that  can  be  used  as  an  etching 
fluid  on  metal. 

MORTISE  —  To  cut  away  parts  of  a  printing-plate  or  block  that 
type  or  other  matter  may  be  inserted  in  it.  It  can  be  an  "  inside  " 
mortise  or  an  "  outside  "  mortise. 

MOUNT  —  The  base  or  support  which  brings  a  printing-plate  to 
type  height. 

MOUNTING  —  The  operation  of  securing  a  printing-plate  to  its 
mount  or  base. 

MULLER  —  An  implement  for  grinding  ink  or  graining  printing 
surfaces. 

MULTIPLE  GRAVER  —  A  graver  for  cutting  several  lines  at  once. 
A  lining  tool. 


THE  PROCESSWORKERS'  GLOSSARY 


215 


NAILING  MACHINE  —  An  improvement  on  the  hand  method  of 
securing  printing-plates  to  their  mounts  or  bases. 

NAIL-PUNCH  —  Used  to  drive  the  head  of  the  blocking  nail  below 
the  printing  surface. 

NATURE  PRINTING  —  A  process  by  which  leaves,  mosses,  feath- 
ers, embroideries  and  the  like  are  pressed  into  a  polished  sheet 
of  lead.  The  lead,  indented  with  their  forms,  is  electrotyped 
and  printed  from  in  a  copperplate  press. 

NEGATIVE  —  Showing  the  lights  and  shades  of  nature  reversed. 

NEGATIVE  DRYER  —  A  place  where  negatives  are  rapidly  dried. 

NEGATIVE  ETCHING  — A  plate  from  which  the  blacks  of  the 
original  copy  will  print  white  and  the  whites  will  print  black. 

NEWSPAPER  CUT  —  The  common  name  for  an  engraving  in  a 
newspaper. 

NEWSPAPER  HALF-TONE  — A  half-tone  made  with  a  coarse 

screen  suitable  for  newspaper  printing. 
NEWS-TONE  —  A  newspaper  half-tone. 

NEWTON'S  RINGS  —  The  colors  which  appear  on  a  polished  metal 
plate  when  it  is  brought  into  intimate  contact  with  a  negative 
in  a  printing-frame. 

NIELLO  —  Engraving  intaglio  and  filling  up  the  incisions  with 
black  or  a  permanent  color. 

NONACTINIC  —  Light  without  effect  on  sensitized  surfaces. 

NON-ACTINIC  —  Term  applied  to  the  safe  light  used  in  dark- 
rooms. 

NORMAL  STOP  —  The  diaphragm  in  half-tone  negative-making 
which  reproduces  the  half-tones  of  the  copy. 

NOTCHING-MACHINE  —  Used  for  cutting  outside  mortises. 

ORIGINAL  —  That  from  which  duplicates  are  made.  Term  some- 
times applied  to  copy  of  any  kind. 

ORTHOCHROMATIC  — Same  as  isochromatic. 

OUTLINED  AND  VIGNETTED  HALF-TONE  — A  half-tone  in 
which  part  of  the  background  is  cut  away  and  part  vignetted. 

OUTLINED  HALF-TONE  —  One  with  the  background  cut  away. 

OUTLINING — Cutting  with  a  graver  a  line  of  separation  between 
an  object  and  its  background. 

OUTSIDE  MORTISE  — To  cut  away  part  of  a  printing-plate  on 
its  outer  edge. 

OVEREXPOSURE  —  A  term  used  when  a  sensitive  surface  is  sub- 
mitted to  the  action  of  light  for  a  longer  period  than  was  correct. 

OVERLAY  —  Paper  placed  over  an  engraving  to  increase  the 
impression  on  certain  areas. 

OXIDATION  —  The  action  of  oxygen  on  the  surface  of  printing- 
plates,  forming  oxids  or  rust. 


216 


horgan's  half-tone 


OYSTER  SHELLS  — A  name  that  well  describes  the  shapes  of 
blemishes  that  occur  on  a  wet-plate  negative  during  development. 

PAD  —  The  elastic  material  at  the  back  of  the  sensitized  plate  in 
the  printing-frame. 

PANCHROMATIC  —  Sensitive  to  all  colors.  Name  given  to  pho- 
tographic plates. 

PANELED  BACKING  —  Mounting  lumber  with  mortised  trans- 
verse end-pieces  for  mounting  large  printing-plates. 

PAPYROTINT  —  A  photolithographic  process  in  which  the  sensi- 
tized gelatin  paper  is  reticulated  after  being  printed  so  that  the 
image  upon  it  is  broken  up  into  a  grain. 

PATENT  BLOCK  —  A  mount  or  support  for  printing-plates  which 
holds  the  plate  secure  by  clamps. 

PATTERN  —  Name  given  to  the  moire  effect  when  screens  or  tints 
are  superimposed  on  one  another. 

PELLICLE  —  Any  thin  film,  such  as  a  collodion  film,  stripped  from 
its  glass  support. 

PEN-AND-INK  —  Term  used  for  a  pen  drawing. 

PHOTO  —  An  abbreviation  of  photograph. 

PHOTOAQUATINT  —  A  photogravure  process  in  which  the  resin- 
ous grain  is  deposited  by  photography. 

PHOTOCHROMOLITHOGRAPH  —  A  lithograph  in  colors,  the 
color  separation  being  made  by  photography. 

PHOTOCHROMOTYPE  — A  picture  in  colors  printed  from  relief 
blocks  made  from  color-separated  negatives. 

PHOTOCOLLOTYPE  — Another  name  for  collotype. 

PHOTOCRAYON  —  A  drawing  made  with  a  crayon  on  a  ground 
glass  laid  over  the  copy.  This  ground  glass  crayon  to  be  after- 
ward reproduced  by  processwork. 

PHOTOELECTROTYPE  —  An  electrotype  from  a  gelatin  relief 
made  by  photography. 

PHOTOENGRAVE  — To  engrave  with  the  assistance  of  light. 

PHOTOENGRAVER  —  One  engaged  in  producing  engravings 
through  the  action  of  light. 

PHOTOENGRAVING  — Term  applied  to  the  production,  by  the 
action  of  light,  of  relief  blocks  for  printing  in  a  typographic 
press.    A  print  from  such  a  block. 

PHOTOETCHING  — An  etching  either  in  relief  or  intaglio  pro- 
duced by  the  action  of  light. 

PHOTOFILIGRANE  — A  photoengraved  plate  for  water-marking 
paper. 

PHOTOGALVANOGRAPHY  —  Electrotyping  from  a  gutta-percha 

relief  made  from  bichromatized  gelatin  exposed  to  light. 
PHOTOGELATIN  —  Another  name  for  collotype. 
PHOTOGLYPHY  —  Engraving  intaglio  by  photography. 


THE  PROCESSWORKERS'  GLOSSARY 


217 


PHOTOGRAVURE  —  An  intaglio  photoengraving  process  which 

reproduces  all  the  tones  of  a  photograph. 
PHOTOLITHOGRAPHY— Producing  printing  images  on  stone 

by  photography.  Making  lithographic  transfers  by  photography. 
PHOTOMECHANICAL  — A   term   applied   to   all  processes  in 

which  photography  is  used  to  aid  the  printing-press. 
PHOTOMETER  —  An  instrument  for  measuring  the  intensity  of 

light.    An  actinometer. 
PHOTOPLANOGRAPHY  —  Photographing  on  metal  plates  for 

surface  printing. 

PHOTO-PROCESS  —  Any  method  of  producing  printing-plates  by 
photography. 

PHOTORELIEF  —  A  photoengraving  for  use  on  the  typographic 
press. 

PHOTOTYPE  — Same  as  photorelief. 

PHOTOXYLOGRAPHY  —  Photographing  on  wood. 

PHOTOZINCOGRAPHY  —  Producing  images  on  zinc  by  photog- 
raphy, either  by  transfers  or  direct  photoprinting  on  the  metal 
for  planographic  printing. 

PLANER  —  A  machine  for  shaving  mounts,  bases  or  printing- 
blocks  to  a  perfect  level. 

PLANOGRAPHIC  PRINTING  —  Printing  from  grained  metal 
plates  in  the  lithographic  manner.  Printing  from  flat  metal 
surfaces. 

PLATE  —  Term  applied  to  a  flat  sheet  of  metal,  glass  or  other 
material  used  in  photoengraving. 

PLATEHOLDER  —  The  dark  slide  that  holds  the  sensitive  plate 
between  darkroom  and  camera. 

PLATE  PLIERS  —  Pliers  with  wide  nose  to  grip  the  edge  of  the 
metal  plate  when  heating  it. 

PLATE  PRINTING  —  Taking  impressions  from  an  intaglio  plate. 

PLAYERTYPE  —  A  negative  on  bromid  paper  produced  by  con- 
tact with  the  copy  in  a  printing-frame. 

POLYCHROMATIC  —  Containing  many  colors.  Sensitive  to  many 
colors. 

POSITIVE  —  A  picture  in  which  the  lights  and  shades  are  as  in 
nature.  In  printed  matter  when  it  is  dark  on  light  paper.  The 
opposite  of  negative. 

POWDER  —  Name  given  to  the  finely  ground  etching  resist. 

POWDER  BOX  —  The  receptacle  for  the  etching  powder  or  pow- 
dered resin  used  as  an  acid  resist. 

POWDERING  BRUSH  —  A  brush  for  removing  the  surplus  etch- 
ing powder  from  a  plate. 

POWDERING  FOUR  WAYS  —  The  act  of  brushing  etching  pow- 


218 


horgan's  half-tone 


der  from  four  directions  against  the  sides  of  lines  or  dots  on  a 
plate. 

PRINT  —  The  image  produced  in  a  printing-frame. 

PRINTING  —  In  photoengraving  is  the  operation  of  getting  an 

image  from  a  negative  or  positive  on  a  surface  sensitive  to  the 

action  of  light. 

PRINTING-FRAME  —  The  frame  used  in  photoengraving  to  hold 
the  negative  or  positive  in  intimate  contact  with  the  sensitized 
surface  during  the  exposure  to  light. 

PRINTING-LAMP  —  The  light  used  before  a  printing-frame. 

PRISM  —  A  triangular  block  of  glass  used  to  produce  reversed 
negatives. 

PROCESS  BLOCKS  —  Any  relief  printing-plate  produced  by  photo- 
engraving. 

PROCESS  CAMERA  —  A  camera  used  by  photoengravers. 

PROCESS  LENS  —  One  giving  sharp  definition,  having  a  flat  field 
and  corrected  for  chromatic  aberration. 

PROCESSWORK  —  Includes  all  the  operations  used  in  photoengra- 
ving and  photomechanical  printing. 

PROOF  —  A  printed  impression  taken  from  a  printing  surface. 

PUNCH  —  A  sharpened  center-punch  for  puncturing  a  printing- 
plate  where  the  blocking  nails  are  to  be  inserted. 

Q UADRICHROMATIC  —  Composed  of  four  colors. 

QUADRICOLOR  —  Photochromotypes  in  which  four  plates  are 
used.  Usually  the  yellow,  red  and  blue,  with  the  addition  of  a 
black,  brown  or  gray. 

RACK  —  A  stand  for  draining  and  drying  negatives,  or  for  holding 
plates  of  any  kind. 

REBITE  —  To  recover  an  engraved  plate  with  an  etching  ground 
and  reetch  it. 

REDUCER  —  A  solution  used  to  reduce  the  density  of  a  negative  or 

reduce  the  width  of  opaque  lines  or  dots. 
REDUCING  —  The  act  of  dissolving  away  some  of  the  opaque  parts 

of  a  negative.  Called  in  half-tone  negative-making  "  cutting." 
REDUCING-GLASS  — A  double  concave  glass  through  which  to 

view  a  picture  to  estimate  its  appearance  on  reduction. 
REDUCTION  —  A  reproduction  of  a  picture  or  object  smaller  in 

size.   The  method  of  reducing  it. 
REETCHING  —  Same  as  rebiting  or  staging. 

REGISTER  —  In  color  reproduction  is  the  making  of  the  different 

color  plates  exactly  the  same  dimensions,  so  that  in  printing  the 

impressions  from  them  will  coincide  perfectly. 
REGISTER  MARKS  —  Small  crosses  or  points  left  on  the  different 

color  plates,  which  when  superimposed  in  printing  produce 

register. 


THE  PROCESSWORKERS'  GLOSSARY 


219 


REPRODUCTION  —  Making  a  copy  by  processwork. 
RESIDUE  —  Waste  material  containing  a  valuable  proportion  of 
silver. 

REVERSED  NEGATIVES  —  Have  the  image  reversed  as  regards 
right  and  left.  Negatives  made  through  a  prism  or  through  the 
glass  support. 

REVERSED  TRANSFERS —  Are  used  on  the  offset  press,  and  are 

reversed  as  regards  right  and  left. 
REVERSING  MIRROR  —  Used  in  place  of  a  prism  for  producing  a 

reversed  negative. 
ROLLING  UP  —  Coating  a  sensitized  or  printing  surface  with  ink 

from  a  roller  prior  to  development,  powdering  or  etching. 
ROTARY  COPY-BOARD  —  A  revolving  copy-board  used  in  color 

plate-making  to  get  the  copy  at  different  angles  in  relation  to 

the  half-tone  screen. 
ROTARY  SCREENHOLDER  — A  device  in  color  plate-making  for 

rotating  the  screen  in  the  plateholder. 
ROUGH  PROOF  —  An  impression  taken  from  a  plate  without  much 

care. 

ROULETTE  —  An  engraver's  tool  containing  a  little  wheel  called  a 

knurl,  and  used  to  lighten  shades  in  a  relief  plate  and  darken 

parts  in  an  intaglio  engraving. 
ROUTER  —  A  machine  for  removing  the  parts  in  the  printing-plate 

not  wanted  in  the  impression.  The  operator  on  such  a  machine. 
SANDPAPERING-MACHINE  —  Used  to  take  the  rough  edges 

from  wooden  mounting-blocks. 
SATURATION  —  When  a  liquid  has  taken  up  all  possible  of  a 

solid. 

SCRAPER  —  A  steel  blade  for  removing  blemishes  in  a  plate  before 
etching.  The  part  of  a  hand  lithographic  press  which  produces 
the  impression. 

SCREENY  NEGATIVE  — One  in  which  the  lines  of  the  screen  are 

unnecessarily  conspicuous. 
SCUM  —  Dirt  on  the  surface  of  a  solution.    Ink,  resin  powder,  or 

anything  which  sticks  to  a  surface  and  prevents  its  being  etched. 
SENSITIZING — Rendering  anything  sensitive  to  the  action  of 

light. 

SEPARATION  —  In  color-record  negative-making  the  dividing  of 
the  primary  color-records  on  to  separate  negatives. 

SHADING-MACHINE  — Used  for  laying  down  tints,  dots,  grains, 
stipples  or  other  textures  on  printing-plates  before  etching. 

SHADOW  STOP  —  The  small  diaphragm  used  in  half-tone  neg- 
ative-making to  produce  white  dots  in  the  deep  shadows. 

SHEARS  —  A  guillotine  for  cutting  metal  plates. 


220 


horgan's  half-tone 


SHOOT-BOARD  —  A  device  with  a  plane  for  squaring  the  sides  of 
blocks. 

SHOULDER  —  The  ledge  which  is  left  in  etching  at  the  sides  of  a 

relief  line  or  dot. 
SIMILIGRAVURE  —  French  term  for  half-tone  engraving. 
SILVER  PRINT  —  A  photographic  print  made  without  toning  on 

a  plain  mat  paper  in  chlorid  of  silver. 
SLUG  —  Photoengravers'  slang  term  for  a  hole  or  scratch  in  a 

negative  film. 

SOFT  —  A  print  giving  all  possible  detail,  both  in  the  high  lights 
and  shadows.   The  opposite  to  contrasty. 

SPENCER  ACID  — A  mordant  for  etching  steel. 

SQUARE  HALF-TONE  — A  half-tone  when  finished  whose  outer 
edges  are  a  rectangle.    Usually  with  a  black  outline. 

SQUARE  INCH  —  The  basis  by  which  photoengravings  are  meas- 
ured. 

STAGING  —  A  method  by  which  an  etcher  stops  out  certain  areas 
in  a  plate  and  continues  the  etching  of  others  so  as  to  produce 
contrasts. 

STAMPING-DIE  —  A  relief  plate  engraved  on  brass  or  zinc  for 
stamping  book-covers  or  similar  surfaces. 

STANNOTYPE  —  A  modification  of  Woodburytype,  in  which  an 
electrotype  is  substituted  for  the  lead  plate. 

STILL-ETCHING  —  Etching  without  movement  of  the  etching 
fluid.    Usually  with  the  plate  face  down. 

STOP  —  Another  name  for  diaphragm. 

STOPPING  DOWN  —  Decreasing  the  aperture  in  the  lens. 

STOPPING  OUT  —  In  etching,  the  covering  up  of  certain  portions 
of  the  plate  with  an  acid-resisting  varnish  to  prevent  further 
etching  of  the  parts  so  covered.  Staging. 

STRIPPING  —  Removing  a  photographic  film  from  its  glass  sup- 
port and  placing  it  upside  down  on  another  support. 

SUBSTRATUM  —  A  coating  on  a  glass  plate  to  make  the  collodion 
adhere  to  it  Used  also  on  metal  to  make  gelatin  and  other  coat- 
ings adhere. 

SWEATING  —  Soldering  a  metal  plate  to  a  metal  body  by  using 
solder  foil  between  the  plate  and  base  and  then  applying  heat 
and  pressure. 

SWELLED-GELATIN  PROCESS  —  An  early  photoengraving  proc- 
ess in  which  a  thick  film  of  bichromatized  gelatin  was  exposed 
to  light  under  a  negative.  The  gelatin  unacted  upon  by  light 
swelled  up  in  cold  water.  A  cast  was  taken  from  it  in  wax,  a 
mold  in  plaster,  and  then  a  cast  in  type  metal. 

THREE-COLOR  PROCESS  PLATES  —  Printing-plates  produced 
from  colored  copy  or  objects  to  reproduce  the  picture  or  object 


THE  PROCESSWORKERS  GLOSSARY 


221 


in  its  original  colors  by  a  photochemical  separation  of  the  pri- 
mary colors,  and  etched  half-tone  plates  to  reproduce  each 
separate  color,  usually  printed  in  yellow,  red  and  blue.  An 
approximate  result  may  be  obtained  from  one-color  copy  by 
using  the  skill  of  the  workmen  in  securing  the  color  values  on 
the  etched  plates. 

THREE  OR  MORE  COLOR  HALF-TONES  —  Same  as  definition 
of  two-color  half-tone,  using  three  or  more  etched  half-tone 
plates. 

TINT-BLOCK  —  A  plate  engraved  in  lines,  dots  or  solid,  to  be 

printed  in  a  faint  color  under  an  illustration. 
TINTYPE  —  A  photograph  on  sheet  iron.   Should  be  ferrotype. 
TOOL  —  Shop  term  for  finishing  a  plate  with  a  graver  or  burin. 
TOP  —  The  acid  resist  on  the  surface  of  the  metal  plate. 
TOPPING  POWDER  — The  first  powder  used  as  an  acid  resist. 
TRANSFER  —  A  print  in  transfer  ink  pulled  either  from  an  intaglio 

or  relief  engraving,  or  made  by  photolithography. 
TRANSFER  INK  —  An  ink  containing  grease,  wax,  resin,  bitumen 

or  any  acid-resisting  substances  used  as  an  etching  ground  or 

in  transferring  pictures  to  stone  or  metal. 
TRANSFER  PAPER  — Paper  coated  with  a  size  of  starch,  gelatin, 

dextrin  or  similar  substances  on  which  a  print  is  made  in  transfer 

ink  for  laying  down  on  stone  or  metal. 
TRICHROMATIC  — Composed  of  three  colors. 
TRIMMER  —  A  machine  for  accurately  dressing  the  sides  of  print- 
ing-blocks. 

TUSCHE  —  A  transfer  ink  for  use  with  a  pen  or  brush  in  lithog- 
raphy or  planography. 

TWO-COLOR  HALF-TONE  — Two  half-tone  plates,  either  or 
both  plates  an  etched  plate  containing  parts  of  the  original 
design,  to  be  printed  in  two  contrasting  colors. 

TYPE-HIGH  GAUGE  —  A  device  for  determining  whether  a  print- 
ing-block is  exactly  the  height  of  type. 

TYPOGRAVURE  —  French  name  for  photoengraving  in  relief. 

UNDERCUT  —  When  the  etching  fluid  has  eaten  beneath  the  edge 
of  the  printing  surface. 

UNDEREXPOSE  —  When  the  action  of  light  on  a  sensitized  sur- 
face has  been  insufficient. 

UNDERLAY  —  Pieces  of  paper  or  other  material  used  under  a 
printing-plate  to  improve  the  quality  of  the  impression. 

U.  S.  P. —  Abbreviation  for  United  States  Pharmacopcea. 

VACUUM  PRINTING-FRAME  —  One  in  which  the  air  is  with- 
drawn from  between  the  plate-glass  front  and  a  sheet-rubber 
back  so  that  the  atmospheric  pressure  on  the  negative  and  sensi- 
tized sheet  is  about  fifteen  pounds  to  the  square  inch. 


222 


horgan's  half-tone 


VIGNETTE  —  An  engraving  having  a  background  that  shades  oft 
to  nothing. 

VIGNETTED  HALF-TONE  — A  half-tone  in  which  one  or  more 
of  the  edges  of  the  object  are  shaded  from  dark  tones  to  pure 
white. 

VIGNETTING  HAMMER  — A  tool  with  a  roughened  face  for 
beating  down  the  hard  edges  of  an  engraving  so  that  it  will 
print  as  a  vignette. 

WASH  DRAWING  — A  drawing  made  with  a  brush  in  a  single 
water-color. 

WASHOUT  PROCESS  — A  name  for  "Leimtype,"  which  see. 
WATER-COLOR  —  A  picture  made  in  colors  soluble  in  water.  An 
aquarelle. 

WAX  ENGRAVING  —  Drawing  with  a  needle  point  and  pressing 
characters  into  a  film  of  wax  on  a  metal  support. .  This  is  after- 
ward electrotyped  to  form  a  printing-plate.  Most  useful  in 
engraving  maps  and  diagrams. 

WET  COLLODION  —  Name  given  to  the  collodion  and  silver  bath 
method  of  making  negatives.  The  plate  so  sensitized  being 
exposed  in  the  camera  while  wet. 

WET  PLATE  —  Term  for  wet  collodion  process  to  distinguish  from 
dry  plate. 

WHIRLER  —  An  apparatus  for  revolving  a  plate  horizontally  in 
order  to  spread  a  solution  evenly  on  its  surface. 

WHITE  LINE  —  A  style  of  wood  engraving  in  which  the  effects  are 
obtained  by  white  lines  instead  of  cutting  around  black  lines. 

WOOD  BASE  —  A  support  or  mount  of  hard  wood  for  the  printing- 
plate. 

WOODBURYTYPE  —  A  picture  in  pigmented  gelatin  printed  from 
a  lead  mold;  the  latter  produced  by  a  photomechanical  process. 

WOODCUT  —  An  engraving  on  wood.   Properly  a  wood  engraving. 

WOOD  ENGRAVER  — One  who  engraves  on  wood. 

WOOD  ENGRAVING  — The  art  of  engraving  on  wood.  A  wooden 
block  so  engraved.   An  impression  from  a  wood  engraved  block. 

XYLOGRAPHY  —  The  original  name  for  wood  engraving. 

ZINC  ETCHING  — A  relief  printing-plate  engraved  on  zinc  by 
etching  fluids. 

ZINC  HALF-TONE  — A  relief  printing-plate  made  from  a  half- 
tone negative  on  zinc. 

ZINC  HOOK  — A  steel  tool  for  cutting  zinc  or  other  metal  sheets 
by  hand. 

ZINCO  —  English  term  for  a  zinc  etching. 
ZINCOGRAPH  — A  photoengraving  on  zinc. 

ZINCOGRAPHY  —  The  process  of  producing  a  photoengraving  on 
zinc. 


INDEX. 


Acidifying  bath  

Acid-proof  powders  

Agar-agar  

Albert   41, 

Albumen  sensitizer  with  glue 

Albumen  substratum  

Albumen    substratum  for 

glass  22, 

Angerer,  Victor  

Aquatint  grain  

Asphaltum  process   

Austrian  etching  process  

Backing  varnish  for  etchers. 

Bichromate  Poisoning,  Rem- 
edies   

Black  specks  on  negatives. . . 

Blackening  agents  35, 

Bleaching  silver  prints.. .  177, 

Blue-print  paper,  to  make. . . 

Blue-prints,  to  bleach  

British  Journal  of  Photog- 
raphy   

Camera  and  lens  

Camera  for  half-tone  

Care  of  the  copy  

Chemical     Symbols  and 

Solubilities   198- 

Chemicals  in  English, 

Latin,  German,  French 
196, 

Chlorid  of  iron  strengths.. 57, 

Chlorid  of  iron,  to  make  

Cleaning  glass  21, 

Coins  for  weights  

Cold  enamel  process  for  zinc 
Collodion  19,  20,  21,  69, 

Half-tone  collodion  

Line  collodion.19,  20,  21,  69, 


PAGE  PAGE 

23  Points  about   70 

176        Special  line   69 

46     Collodion  bottles    30 

127     Collodion  emulsion  or  dry 

165          plates    158 

157     Collodion  formulas  

19,  20,  69,  70,  90,  91 
157     Collodion  formula,  To  re- 

49          member    19 

175     Collodion,  when  old   158 

165     Collodionizing  and  sensitiz- 

169          ing   30 

Colloids   Used  —  Gelatin, 

172          Isinglass    46 

Collotype   41-45 

180       Coating  glass  plates   42 

159        Collotype  presses   45 

36        Collotype  results   45 

178  Different  names  for   41 

179  Drying  the  sensitive  coat- 
*79             ing   43 

Inking  collotype   45 

36        Etching  and  printing   44 

Negative  and  printing   44 

24  Principle  of  collotype   41 

88        Sensitive  coating   43 

28        Substratum  for  collotype..  42 

Timing  exposure   44 

•199     Color-sensitive  plates  113, 

120,  121,  122,  123,  124,  158 
Color  vision,  color  blindness.  111 

197     Copper,  cleaning  54,  55 

58     Copper  cylinders  146,  147, 

T72  148,  149,  150 

T57     Copper  etching  106,  107 

I7I     Copperplating  zinc   176 

Copper  roll  engraving  50,  51 

70     Copper  rolls  to  etch   150 

Copy  board   26 

70     Copyright  law  penalties   188 

223 


horgan's  half-tone 


224 

PAGE 

Cost  records  on  Graphic   12 

Cutting     solution  destroys 

gradation   19 

Cyanotype  paper,  to  make. . .  179 

Daguerre,  L.  J.  M   50 

Daguerreotyping  on  copper 

roll    153 

Dampening  box  for  transfer 

paper   39 

Dargavel,  A.,  screen   89 

Darkroom  ventilation,  etc   164 

Desensitizing   solutions  for 

offset   141,  142 

Developer  containing  gelatin  31 

Development  principles  

Development,  Proper  method  32 
Direct  method  of  colorwork.  118 
30,  31,  32,  33 

"  Direct  Process  "   189 

Dragon's-blood    172 

Dragon's-blood  powder-box.  169 
Dry  plates  in  processwork. .  163 
Drying,  To  keep  plate  from.  30 
Dry  enamel  process   166 

Edwards,  Ernest   41,  42 

Egloffstein,  Gen.  F.  W.  von, 

screen   89 

Electric  lighting    27 

Enamel  formulas  

102,  103,  109,  166,  168 
Engraver  and  Printer,  Mar., 

'93    112 

Engravers'   and  Printers' 

Exhibits   5-10 

Equivalent  focus,  to  find   156 

Etching  baths  for  zinc   170 

Etching  ink,  waxes,  resins. . .  174 

Etching  the  negative   184 

Exposure  Effected  by  Cam- 
era Extension  and  Dia- 
phragm   200 

Exposure,  to  find  94,  95 

Facts  for  Process  Photog- 
raphers 155-164 


PAGE 

Fathers  of  photolithography.  11 
Fathers  of  three-color  work..  111 


Finishing   107,  108 

First  illustrated  daily  paper..  12 

Fish  glue   171 

Fixing  the  negative   34 

Focusing    29 

Fog  and  its  causes   161 

For    Foremen,  Finishers, 

Journeymen   171-176 

Formulas  : 


Acetic  acid  for  stripping.  .  73 
Albumen  for  offset  work...  138 
Albumen  sensitizer  for  zinc  75 
Albumen    sensitizer  with 


glue   165 

Albumen   substratum  for 

glass  22,  157 

Asphalt  developer   139 

Asphalt  for  offset  work. . .  138 

Asphalt  process   165 

Bichromate  poisoning,  salve  180 

Blackening  solution  35,  97 

Blackening  zinc   190 

Bleaching  silver  prints.  177,  178 

Blue-print  paper   179 

Carbon  tissue  sensitizer...  55 

Chlorid  of  iron  "172 

Cold  enamel   168 

Collodion  for  half-tone. 90,  91 
Collodion  for  line  work. 20,  69 

Collodion,  stripping   72 

Collotype  etching  solution.  45 

Collotype  sensitizer    43 

Collotype  substratum   42 

Copper  etching   106 

Copper  intensifier   71 

Copper-plating  zinc   176 

Cutting  solution   96,  97 

Cyanin  resensitizer    122 

Cyanotype  paper   179 

Desensitizing  solutions.  141,  142 
Developer  with  gelatin. ...  31 

Dry  enamel   166 

Drying,  preventing    no 


INDEX 


225 


PAGE 

Dye  bath,  developed  image  139 

Dye  for  enamel   104 

Enamel  for  half-tone.  .102,  109 
Enamel  for  rotary  photo- 
gravure   153 

Enamel  for  zinc   83 

Enamel,  Ives'   109 

Enamel  with  hardener   83 

Etching  baths,  zinc  

79,  80,  81,  170 

Etching  copper   106 

Etching  solutions,  photo- 
gravure   58 

Etching  steel   59 

Glass-cleaning  21,  157 

Graining  bath  for  zinc . .  74,  82 

Graining  material   136 

Graining  offset  zinc   135 

Green  sensitizer   123 

Gum  solution  for  zinc   143 

Half-tone  collodion  90,  91 

Half-tone  enamel  102,  109 

Hardener  for  zinc  enamel.  84 

Intensifier,  copper   71 

Intensifies  iodin   36 

Intensifier,  lead   160 

Intensifier,  mercury   35 

Intensifier,  mercury-iodid.  34 

Intensifier,  Schlippe's  salt.  164 

Iodid  substitutes    163 

Iodin  intensifier   36 

Ives'  enamel   109 

Lead  intensifier   160 

Line  collodion   20,  69 

Magnesia,  to  remove   173 

Mercury  intensifier   35 

Mercury  mordant  for  steel  59 

Moss  process   61 

Nonhalation  backing   121 

Offset,  asphalt  coating   138 

Offset  press  desensitizers.. 

141,  142 

Offset  sensitizer   138 

Ointment  for  bichromate 

sores   180 

15 


PAGE 

Photoelectrotype  gelatin.. .  65 
Photographing  on  wood.. .  177 
Photogravure  rolls,  to  pre- 
pare   149 

Photolith  paper   14 

Pinachrome  resensitizer  . . .  123 
Pinacyanol  resensitizer  . . .  122 

Plain  photo-paper   178 

Poison  antidotes  194,  195 

Preservative  for  developed 

plates    159 

Red  sensitizer  122,  123 

Reducing,  cutting  solution. 

96,  97 

Resensitizing  color  plates..  122 

Retouching  varnish   173 

Rotary  photogravure 

enamel    153 

Rotary  photogravure  sub- 
stratum   149 

Rubber  solution   72 

Safe  lights,  to  make   119 

Salve  for  bichromate  sores  180 
Schlippe's  salt  intensifier . .  164 
Screen  angles,  four-color..  131 
Screen  angles,  three-color.  127 

Screenmaking  varnish   183 

Scum  removal  105,  106,  166 

Silver  bath    22 

Special  line  collodion   69 

Spencer  acid  for  steel   59 

Steel-facing  copper   60 

Stopping-out  varnish   175 

Stripping  collodion   72 

Stripping  rubber   72 

Swelled  gelatin   61 

Vandyke  process   144 

Varnish,  acid-resist   172 

Varnish  for  screenmaking.  183 

Varnish,  retouching   173 

Varnish,  stopping-out  ....  175 

Washout  gelatin   65 

Wood,  to  photograph  on. .  177 

Zinc,  cold  enamel   168 

Zinc  enamel   83 


226 


horgan's  half-tone 


PAGE 

Zinc  enamel  with  hardener  83 

Zinc  etching  baths  

79,  80,  81,  170 

Zinc  graining  bath  74,  82 

Zinc,  graining  for  offset...  135 

Zinc  sensitizer   75 

Zinc,  to  blacken   190 

Zinc,  to  copperplate   176 

Zinc,  to  roll  up   143 

Fourth  plate  in  colorwork. . . 

114,  118 
Four-color  Blockmaking.  . 

111-132 

Fox-Talbot,  W.  H. .  47, 48, 49,  5* 
French  into  English  Meas- 
ures   192 

French  into  English 

Weights    192 

Gamier  process   no 

Gelatin  43,  46 

Gelatin  preservative   46 

Gelatin  sensitive  to  chrome 

alum    15 

Gelatin,  To  extract  grease. . .  15 

Glass-cleaning  21,  157 

Glossary  of  Process  Terms. 

201-222 

Graining  machine  for  offset 

press   135 

Graining  machine  marbles . . .  135 

Graining  machine  principle. .  134 
Graining  machine  scratching 

material   136 

Gum  arabic  varnish   37 

Goupil   48 

Government  money  or  stamps  188 

Grained  zinc  and  litho  stone  133 

Greeley,  Horace    64 

Ground  glass  substitute   156 

Halation  and  remedies   121 

Half-tone  borders   160 


FACE 

Half  -  tone  Engravers 
Should  Know   109 

Half-tone  Engraving  85-110 

Another  reduction  method.  97 

Blackening  negative   98 

Brush  little   107 

Brushing  away  umbrellas.  107 

Burning-in  enamel   105 

Business  dependent  on  it. .  86 

Chamfering  edges   108 

Chlorid  of  iron.   106 

Chlorid  of  iron  to  make.. .  172 

Cleaning  screens   185 

Coating  with  enamel . .  103,  104 

Cold  enamel  for  zinc   168 

Collodion  ,%  90,  91 

Contrasty  half-tone   98 

Cooling  copper    105 

Copper  preparation   103 

Cutting  solution  96,  97 

Dargavel,  A.,  screen   89 

"  Demi-teinte  "   85 

Developing  enamel   104 

Development    101 

Diaphragm  numbers    155 

Diaphragms,  stops  

91,  92,  93,  100 

Dry  enamel   166 

Egloff stein,  Gen.  F.  W.  von, 

screens   89 

Elliptical  diaphragms    126 

Enamel  102,  103,  109 

Enamel  formula  102,  109 

Enamel  thickness  102,  103 

Etching  106,  107 

Examining  dots   107 

Exposure  records   95 

Exposure  table    200 

Factors    99 

Finishing,  reetching   107 

Fish  glue   171 

Fixing    101 

Flashing    98 

Flat  half-tone    98 

Gamier  process   no 


INDEX 


227 


Getting  it  in  the  negative..  91 

Grain  screens   88 

Gray  borders   160 

"  Halbtoneprozess  "    85 

Half-tone  principles. . .  .98,  99 

High-light  half-tones   144 

High-light  stop   93 

Horgan  stops   100 

How  to  distinguish  half- 
tone   86 

Ideal  collodion    90 

Importance  of   85 

In  hot  weather   109 

Intensification   101 

Intensifying  71,  72,  160,  184 

Inventor  of  enamel   no 

Ives'  enamel  formula   109 

Ives,  Frederick  E.,  screen 

1885-86   87 

Levy,  Max,  screen,  1893 . .  87 

Light  necessary   89 

Local  reduction   97 

Machine  etching   106 

Magnesia  removal    173 

Methyl  violet   104 

Mezzograph  screen   186 

Mezzograph  screen  most 

useful    186 

Most  intricate  work  87,  88 

Newspaper  half-tones   89 

Normal  diaphragm   92 

Origin  of  "Half-tone"....  85 

Overexposure   105 

Perfect  apparatus  required  88 

Pointers    99 

Printing  enamel   104 

Proper  exposure   94 

Proving,  beveling,  etc   108 

Purton,  Chas.  E   no 

Reducing  or  cutting  96,  97 

Relations  of  factors   99 

Retouching  varnish   173 

Routing,  blocking  108,  109 

Screen  distance.  .92,  93,  95,  99 
15a 


Screen  distance  and  expos- 
ure   95 

Screen  facts   185 

Screen  sections   154 

Screen  sweating   185 

Screeny  effect   88 

Scum  on  enamel  prints   166 

Scum  removal  105,  106,  166 

Shadow  stop   93 

Shapes  of  apertures   100 

"  Similigravure "    85 

Stain  removal    108 

Staining  with  dye   104 

Still  etching   106 

Still-etching  principle. .  106,  107 

Stopping-out  varnish   175 

Stripping  films  72,  73,  74 

Theories  omitted  here   87 

The  screen   87 

Trial  exposures   94 

Tub  etching   107 

Undercutting    107 

Vignetting   108 

Waterhouse,  Ma j. -Gen   no 

Wavy-line  screens   89 

What  is  a  half-tone?   86 

When  to  stop  etching   107 

Hascher's   rotary  photo- 
gravure   153 

High-light  half-tones   144 

Horgan,  S.  H   187 

Horgan  stops   100 

Husnik  41,  63,  64 

Huson,  Thomas   60 

Illumination  of  copy  27,  28 

Importance  of  half-tone  busi- 
ness   85 

Indirect  method  of  colorwork  118 

Increasing  exposure   159 

Intensification   

34,  35,  36,  71,  72 

Iodizing  bath   23 

Iron  developer,  strength.  .30,  31 
Isinglass   46 


228 


horgan's  half-tone 


PAGE 

Ives,    Frederick   E.,  color- 
work   112,  127 

Ives.  Frederick  E.,  screen...  87 

Key-plates,     To  Photo- 
graph on  Zinc   190 

Klic,  Carl  48,  49,  50,  51 

Lead  intensifier   160 

Leimtype   63 

Levy,  Max.,  screen   87 

Lighting  copy  27,  28 

Lithographer  for  collotype..  44 

Litho  Roller,  Its  Care   181 

Litho  roller  preparation   181 

Lemercier   41 

Magnesia,  to  remove   173 

Mercury  mordant  for  steel..  59 

Mertens,  Dr.  Eduard  150-152 

Metric  Measures  into  Eng- 
lish   192 

Mezzograph  screen    186 

Mezzograph  screen  is  most 

useful    186 

Moss,  John  A  61,  62 

Moss  Process  61-62 

Mothay,  Tessier  du   41 

Mutilation  of  copy   155 

Negative,  overcut,  to  restore  160 

Negative  retouching  52,  53 

Negative  retouching  37,  38 

Negative  varnish   37 

Negatives  Etched  by  Hand. 

183-185 

New  York  Daily  Graphic... 

11,  12,  13,  27,  36 

Niepce,  J.  N   47 

Norwich  film   189 

Numbering  diaphragms   155 

Obernetter   41 

Offset  Press,  Photography 

133-144 


PAGE 

Desensitizing  solutions. 141,  142 

Developing  with  turps   139 

Enamel  for  offset   140 

Exposure  to  light   139 

Graining  machine.  135,  136,  137 

Graining  pointers   137 

Graining  zinc  by  hand   134 

Gumming-up  grained  zinc. 

141,  143 

High-light  negatives   144 

How  zinc  holds  water   133 

Information  for  offset 

work   142,  143 

Marbles  used  135,  136 

Photolith  applied  to  offset.  133 
Photoprint  on  grained 

metal   137 

Protective  varnish  for  ship- 
ping   140 

Regraining    137 

Scratching  material   136 

Sensitizing  grained  zinc. . .  138 

Shipping  the  plate   140 

Sponges  must  be  clean   142 

Staining  the  image   139 

Vandyke  process   144 

Zinc  and  litho  stone. .  .133,  134 

Zinc  for  offset  press   134 

Offset  press  revives  photolith  11 
Oils  in  transfer  ink   174 

Parallelism  necessary   29 

Penrose's  Annual   32 

Photoelectrotype  Process. 63-68 

Brushes  used   66 

Cases  for  molding  sheets. .  65 

Composition  of  gelatin   64 

Double  wash-out    64 

Encyclopedia  Britannica  .  63 

Formula  for  gelatin   65 

Husnik's  patent  63,  64 

Large  editions  printed   68 

Leimtype   63 

Making  the  sheets   65 

Mumler's  patent,  1875.. 63,  64 


INDEX 


PAGE 

Permanent  support   67 

Principle  of  process   63 

Printing  the  image   66 

"  Rotting  "  the  gelatin   64 

Second  wash-out   67 

Securing  to  support   63 

Shellac  used   67 

Single  wash-out    63 

Stripping  the  film   67 

Trays  necessary   66 

Wash-out  process    63 

Washing  out   66 

Webster's  Unabridged   63 

Photograph   key  -  plates  on 

zinc   190 

Photograph  paper,  to  make. .  178 
Photographers  Should 

Know  155-164 

Albumen  substratum   157 

Collodion,  when  old   158 


Darkroom  ventilation   164 

Diaphragm  numbering   155 

Dry  plates  in  processwork.  163 

Emulsion  or  dry  plates   158 

Equivalent  focus  of  a  lens  156 


Fog  and  its  causes   161 

Glass-cleaning    157 

Half-tone  borders   160 

Increasing  exposure   159 

Lead  intensifier   160 

Negatives  with  black  specks  159 

Photographing  silverware.  157 

Pinholes  in  negatives   162 

Preservation  of  copy   155 

Preservative  for  developed 

plates    159 

Restoring  overcut  negative  160 

Schlippe's  salt  intensifier. .  164 

Silver  bath,  to  purify   162 

Substitute  for  ground  glass  156 

Substitutes  for  iodid   163 

Photographic  News   no 

Photographing  by  steam   36 

Photographing  on  wood   177 

"Photography  in  Colors"...  112 


229 

PAGE 

Photogravure   47-60 

Angerer,  Victor   49 

Asphalt  for  graining   55 

Bitten  plates   48 

Carbon  process  necessary..  51 

Carbon  tissue   52 

Carl  Klic's  improvements.. 

48,  49,  51 

Chlorid  of  iron  strengths. .  58 

Copper  preparation   54 

Developing  the  image   57 

Drying  the  tissue  56,  57 

Electrotyping  daguerreo- 
types   50 

Etching    58 

Etching  solutions  required.  57 

Fox-Talbot  the  inventor . .  47 

Goupil  method   48 

Government  maps   51 

Grain  direct  on  copper   49 

Graining  box   53,  54 

Graining  the  plate   55 

Grown  plates   48 

Heating  the  ground   55 

Mariot  of  Vienna   51 

Negative  most  important..  52 

Photogravure  maps,  1869..  51 

Pretsch's  patent,  1854-55. . .  50 

Proving  and  reetching   58 

Reetching   58 

Retouching  negative   53 

Reversed  transparency   53 

Rotary    photogravure  in 

1854    50 

Sensitizing  the  tissue   55 

Steel  facing  59,  60 

Talbot's  patent,  1858   47 

Timing  the  exposure   56 

Two  methods  of  photogra- 
vure   48 

U.  S.  Govt,  maps   51 

Photolithography   11-40 

Albumen  substratum   22 

American  Photolith  Co —  12 


230 


horgan's  half-tone 


PAGE 

Apparatus     for  coating 

paper   15 

Camera  and  lens   24 

Care  of  copy  28,  155 

Collodion   19 

Collodionizing  large  plates.  21 

Cutting  &  Bradford  patent.  12 

Developing  transfers   40 

Development    30 

Dixon  and  Lewis  11,  12 

Drying  coated  sheets   17 

Drying  transfers   40 

Electric  lighting   27 

Fathers  of   11 

Fixing  the  negative   34 

Focusing    29 

Free  silver  necessary   33 

Gelatin  in  developer   31 

Get  it  in  the  negative   32 

Glass-cleaning    21 

Graphic  process,  inexpen- 
sive   12 

How  to  develop   32 

Illumination  of  copy   27 

Inking  the  paper   39 

Instructions  for  coating. . .  18 

Intensification    34 

Iodin  intensifier   36 

Largest  establishment   11 

Lemercier,  Lerebours,  Da- 

vanne    12 

Line  collodion  formula   20 

Mercury  intensifier    35 

Negative-making   28 

Negative  required   19 

Offset  press  revives  it   11 

One-man  device  for  coating  16 
Osborne,  J.  W.,  of  Mel- 
bourne   12 

Photographing  by  steam . .  36 

Photolith  transfer    38 

Poitevin's  1855  patent   12 

Practiced  in  secret   11 

Preparing  sensitizer   14 

Protecting  the  negative...  37 


PAGE 

Retouching  the  negative..  37 

Sensitizing,  exposing   30 

Sensitizing  solution  for...  14 

Silver  bath   22 

Temperature,  coating-room  17 

The  coating-room   17 

The  ideal  transfer   13 

The  paper  to  use   14 

Transfer  ink    39 

Photoplanographic  process  .  13 

Photoplanography   133-144 

Photoplanography  informa- 
tion   142 

Pinholes  in  negatives   162 

Planographic  printing  from 

zinc   11 

Pointers  for  Photograph- 
ers  177-179 

Poisons  and  Antidotes.  .  194,  195 

Poitevin,  Louis  A  12,  41,  50 

Preservative  for  developed 

plates    159 

Pretsch,  Paul   50 

Printing  on  large  stones   182 

Printing  without  a  frame   182 

Process  Photogram   152 

Process  workers'  Glossary  

201-222 

Processworkers  May  Be 

Jailed   187 

Purifying  bath   23 

Purton,  Chas.  E   110 

Reducing,  or  cutting.. 96,  97,  98 
Reflections  must  be  guarded 

against   29 

Relief  Line  Engraving  69-84 

Acetic  acid  bath   73 

Albumen  preparation   75 

Albumen  sensitizer   75 

Albumen  substratum   22 

Blackening  agents  35,  36 

Blotting  and  drying   74 

Camera  and  lens   24 

Collodion  formula   70 


INDEX 


Contrasty  collodion   69 

Copper  intensifier  70,  71 

"  Cutting  "  destroys   69 

Developer  30,  31,  32,  34 

Developing  image  on  zinc.  77 

Drying  developed  print   78 

Drying  films   73 

Enamel  for  zinc  82,  83,  84 

Etching  machines   81 

Etching  zinc  79,  80,  81 

Exposure  necessary   77 

Finisher's  work   82 

First  bite   79 

Fixing  negative   34 

Fourth  bite   81 

Graining  bath   74 

Graining  bath  for  zinc . .  74,  82 

Glass-cleaning  21,  157 

Heat  to  melt  resin   79 

Ink  used   77 

Inking  zinc   77 

Intensification    70 

Lighting  copy   27 

Little  improvement  in   69 

Melting  powder   79 

Negatives  for  relief  work..  71 

Negative  turners   74 

Newspaper  stripping   73 

Points  about  collodion   70 

Potash  to  clean  plate   82 

Powdering  four  ways..  .80,  81 

Powdering  the  plate   78 

Preparation  of  collodion. . .  70 

Preparing  metal   74 

Printing  on  zinc   78 

Removing  acid  resist   81 

Retouching  print   78 

Retouching  the  negative. . .  37 

Roller  used   77 

Rubber  solution   72 

Second  bite   80 

Sensitizing  zinc   76 

Silver  bath   70 

Special  line  collodion..  .20,  69 


231 

PAGE 

Stripping  and  reversing. . . 

72,  73,  74 

Stripping  collodion   72 

"  Topping  "  powder   78 

Varnishing  back  of  zinc. . .  79 

Zinc  enamel  with  hardener  83 

Zinc  preparation   74 

Zinc  sensitizer   75 

Rembrandt  Intaglio  Printing 

Co  145,  146 

Resensitizing  dry  plates  

122,  123,  124 

Retouching  varnish    173 

Reversed  negatives   25 

Photographing  through 

glass    25 

Stripping  and  turning   25 

With  mirrors  and  prisms..  25 

Roche,  T.  C  41,  42 

Rotary  Photogravure.  . .  145-154 

Carbon  tissue   148,  149 

Cleaning  resist  from  roll. .  150 

Cylinders,  kinds  of   147 

Daguerreotyping  on  roll.. .  153 

Developing  tissue   149 

Etching  the  copper  roll   150 

First  description,  1897   145 

Freiburger  Zeitung   150 

Half-tone  enamel    152 

Hascher,  J.  M.,  his  method  153 

Inland  Printer,  1908   145 

Klic  and  Klisch  screens. . .  146 

Klisch   146 

Local  development   150 

Marinoni  built  press   145 

Mertens,  Dr.  Eduard   150 

Mertens'  image  on  cylinder  152 

Mertens'  method   151 

Mertens'  negative  and  pos- 
itive   151 

Other  methods   150 

Potters  use  steel  blade   145 

Preparing  the  cylinder   148 

Principle  of  process . . .  146,  147 

Process  Year  Book,  1897. .  145 


232 


HORGAN  S  HALF-TONE 


PAGE 


Rembrandt  Co.'s  work. .. .  145 

Rotary  and  flat-printed   146 

Saalburg,  Chas.  W   146 

Screen  for  process   154 

Screen  lines  on  cylinder. . .  147 

Screens  and  their  use   148 

Substratum  on  cylinder. . .  149 
The  doctor   145 


Transferring  enamel  to  roll 

152-153 

Transferring  printed  tissue  149 

Villain,  A.,  his  method   152 

Rotary  photogravure  first 

practiced    145 

Rotary  photogravure  methods  150 
Rotary  photogravure  pioneers 

145,  146 

Rotary  photogravure  screen.  154 

Saalburg' s  accomplishment . .  146 

Safe  lights  for  development. .  119 

Sawyer   41 

Schlippe's  salt  intensifier   164 

Scientific  work   184 

Screen  angles  for  four  colors  128 

Screen  angles  for  three  colors  127 

Screen  distance  92,  93 

Screen  facts   185 

Screen  sweating,  preventive.  185 
Screens  and  Their  Care.. 

185-186 

Screens,  to  clean   185 

Scum  on  enamel  prints   166 

Sensitizing   with   nitrate  of 

silver   30 

Shipping  offset  plates   140 

Sigsbee,  Capt.  CD   51 

Silver  bath  preparation   22 

Silver  bath,  to  purify   162 

Silverware  to  photograph. . .  157 
Solubilities   of  Principal 

Chemicals    199 

Solution  for  steel  facing   60 

Spencer  acid  for  steel   59 

Spirit  photography  humbug.  64 


PAGE 


Sprague   41 

Steel,  etching   59 

Etching  with  mercury   59 

Etching  with  Spencer  acid.  59 

Spencer  acid   59 

Steel  facing  copper   60 

Stopping-out  varnish   175 

Sfops  for  half-tone  

92,  93,  100,  126 
Stripping  and  reversing  neg- 
atives   72 

Substitutes  for  iodids   163 

Swelled  Gelatin  Relief   61 

Drying  printing  and  swell- 
ing   61 

Gelatin  solution  for   61 

Ground  glass  supports   61 

Molding  and  casting   62 

Moss  process   61 

Peculiarities  of  engraving.  62 
Swelled  Gelatin  Process..6i-62 

Taylor,  J.  Trail   36 

Theory  of  color  screens   114 


Thermometer  Comparisons.  193 
Three-color  Processwork.  . 

111-132 

Albert's  eoside  of  silver...  121 
Angles  for  four  color..  128,  131 


Apochromatic  lens   116 

Camera  with  circular 

screen   128 

Chart,  to  test  a  lens   116 

Clerk-Maxwell  in  1855   ill 

Collen,  1865   in 

Collodion  emulsion  in  pow- 
der   120 

Color  patches   125 

Color-record  negatives  ...  113 

Color-sensitive  plates   120 

Color-separation  negatives.  113 
Color-vision    should  be 

normal   ill 

Cramer  dry  plates   121 

Cyanin  formula   122 


INDEX 


233 


PAGE 

Development   130 

Development,  safe  light...  119 
Elliptical  diaphragms. .  125,  126 

Emulsion  or  dry  plates   158 

Etching  color-plates  ..   131 

Exposing  color-record  neg- 
atives   129 

Exposure  periods   124 

Fathers  of  three-color   111 

Fourth  plate  114,  118 

Halation    121 

Half-tone  negative   131 

Hauron,  L.  D.  du,  1859. 1 11,  127 
Indirect  and  direct  meth- 
ods   118 

Ives,  Frederick  E   112 

Kurtz,  William,  1892...  112,  127 

Lens  and  camera   115 

Light  for  three-color.  .114,  115 
Moire,  to  avoid...  125,  126,  127 

Nonhalation  backing   121 

Pattern,  to  prevent   127 

Pinacyanol    122 

Pinachrome  sensitizer   122 

Points  in  resensitizing   124 

Practice  versus  theory   114 

Printing  three-color   132 

Procedure   129 

Ransonnet,  Baron,  1865...  ill 

Record-keeping   124 

Reduction,  intensification..  130 

Resensitizing    122 

Screen  angles   127 

Screens  for  three-color   128 

Sillib  &  Bruckman   121 

Theoretical  sensitive  plates  113 

Theory  of  color  filters   114 

Theory  of  three-color.  112,  113 

The  positives   131 

Three-color   filters  or 

screens   117 

Ulrich  in  Berlin   112 

Vogel,  Dr.  H.  W.,  1873...  112 
Wratten  &  Wainwright. . .  121 


PAGE 

Transfer  ink   39 

Transferring   Enamel  to 
Roll   1 53-154 

Unfit  for  publication.   187 

Vandyke  process   144 

Varnish  for  plate  backing. . .  172 

Varnish  for  retouching   173 

Varnish  for  screenmaking. . . 

183,  184 

Varnish  for  stopping-out   175 

Villain,   A.,    rotary  photo- 
gravure   152 

Violet  rays  injure  eyesight. .  180 

Waterhouse,    Maj.-Gen.  J. 

41,  51,  no 

Weights  and  Measures   191 

Weights  and  measures  point- 
ers   171 

Weights  of  sheet  metals   190 

What  is  a  half-tone?   86 

Wood  engraving,  cost   179 

Wood,  to  photograph  on   177 

Yellow  stain   35 

Zinc  and  Copper  Etcher's 

Formulas  165,  170 

Acid-proof  powders   176 

Albumen    sensitizer  with 

glue   165 

Another  cold  enamel   168 

Asphalt  process   165 

Austrian  etching  method. .  169 

Bichromate  poisoning   180 

Cold  enamel  for  zinc   168 

Copper-plating  zinc   176 

Dragon's-blood    172 

Dragon's-blood  box   169 

Dry  enamel  process   166 

Fish  glue   171 

Key-plates  on  zinc   190 


234  horgan's 

PAGE 

Oils  used  in  transfer  ink. .  174 

Prevent  zinc  oxidation   175 

Retouching  varnish    173 

Scum  on  enamel  prints   166 

Stopping-out  varnish   175 

Strength  zinc  baths   170 

Varnish  for  plate  backing.  172* 


HALF-TONE 

PAGE 

Waxes  and  resins  in  ink..  174 
Weights  of  sheet  metals..  190 
Zinc  ruined  by  overheating  167 
Zinc  ruined  by  overheating. .  167 
Zinc  for  offset-press  work..  134 
Zinc  oxidation,  to  prevent. . .  175 
Zinc  sensitizer  75,  82,  83,  84 


J GETTY  RESEARCH  INSTITUTE1 


